diff --git a/basic-geometry-dev/main.c b/basic-geometry-dev/main.c
index 06bb601..b1f5468 100644
--- a/basic-geometry-dev/main.c
+++ b/basic-geometry-dev/main.c
@@ -1,3 +1,4 @@
+/*
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>
@@ -59,7 +60,7 @@ structure_fp32_t* make_structures(const unsigned int amount)
         );
 
         bgc_vector3_reset_fp32(&list[i].vector2);
-        */
+        *//*
     }
 
     return list;
@@ -137,23 +138,16 @@ int main()
 }
 */
 
-//#include <stdio.h>
-//#include <basic-geometry.h>
-
 #include <stdio.h>
 #include <basic-geometry.h>
 
 int main()
 {
-    BgcVector3FP32 my_vector1, my_vector2;
+    BgcVector3FP32 my_vector;
 
-    bgc_vector3_set_values_fp32(-2, 7, 5, &my_vector1);
-    bgc_vector3_set_values_fp32(10, -1, -3, &my_vector2);
+    bgc_vector3_set_values_fp32(-2, 7, 10, &my_vector);
 
-    bgc_vector3_swap_fp32(&my_vector1, &my_vector2);
-
-    printf("Vector #1: x1 = %f, x2 = %f, x3 = %f\n", my_vector1.x1, my_vector1.x2, my_vector1.x3);
-    printf("Vector #2: x1 = %f, x2 = %f, x3 = %f\n", my_vector2.x1, my_vector2.x2, my_vector2.x3);
+    printf("x1 = %f, x2 = %f, x3 = %f\n", my_vector.x1, my_vector.x2, my_vector.x3);
 
     return 0;
 }
diff --git a/basic-geometry/basic-geometry.h b/basic-geometry/basic-geometry.h
index 7a608d8..5a3923c 100644
--- a/basic-geometry/basic-geometry.h
+++ b/basic-geometry/basic-geometry.h
@@ -14,7 +14,7 @@
 #include "matrix3x2.h"
 #include "matrix3x3.h"
 
-#include "tangent.h"
+#include "tangent-pair.h"
 
 #include "rotation3.h"
 
diff --git a/basic-geometry/basic-geometry.vcxproj b/basic-geometry/basic-geometry.vcxproj
index 8a228bb..98620b5 100644
--- a/basic-geometry/basic-geometry.vcxproj
+++ b/basic-geometry/basic-geometry.vcxproj
@@ -28,7 +28,7 @@
     <ClInclude Include="matrixes.h" />
     <ClInclude Include="quaternion.h" />
     <ClInclude Include="rotation3.h" />
-    <ClInclude Include="tangent.h" />
+    <ClInclude Include="tangent-pair.h" />
     <ClInclude Include="utilities.h" />
     <ClInclude Include="versor.h" />
     <ClInclude Include="vector2.h" />
@@ -44,7 +44,7 @@
     <ClCompile Include="matrixes.c" />
     <ClCompile Include="quaternion.c" />
     <ClCompile Include="rotation3.c" />
-    <ClCompile Include="tangent.c" />
+    <ClCompile Include="tangent-pair.c" />
     <ClCompile Include="versor.c" />
     <ClCompile Include="vector2.c" />
     <ClCompile Include="vector3.c" />
diff --git a/basic-geometry/basic-geometry.vcxproj.filters b/basic-geometry/basic-geometry.vcxproj.filters
index 2cb8892..2349250 100644
--- a/basic-geometry/basic-geometry.vcxproj.filters
+++ b/basic-geometry/basic-geometry.vcxproj.filters
@@ -54,7 +54,7 @@
     <ClInclude Include="matrixes.h">
       <Filter>Файлы заголовков</Filter>
     </ClInclude>
-    <ClInclude Include="tangent.h">
+    <ClInclude Include="tangent-pair.h">
       <Filter>Файлы заголовков</Filter>
     </ClInclude>
   </ItemGroup>
@@ -95,7 +95,7 @@
     <ClCompile Include="matrix3x2.c">
       <Filter>Исходные файлы</Filter>
     </ClCompile>
-    <ClCompile Include="tangent.c">
+    <ClCompile Include="tangent-pair.c">
       <Filter>Исходные файлы</Filter>
     </ClCompile>
   </ItemGroup>
diff --git a/basic-geometry/tangent-pair.c b/basic-geometry/tangent-pair.c
new file mode 100644
index 0000000..e0bce76
--- /dev/null
+++ b/basic-geometry/tangent-pair.c
@@ -0,0 +1,82 @@
+#include "tangent-pair.h"
+
+const BgcTangentPairFP32 BGC_IDLE_TANGENT_PAIR_FP32 = { 1.0f, 0.0f };
+
+const BgcTangentPairFP64 BGC_IDLE_TANGENT_PAIR_FP64 = { 1.0, 0.0 };
+
+extern inline void bgc_tangent_pair_reset_fp32(BgcTangentPairFP32* tangent);
+extern inline void bgc_tangent_pair_reset_fp64(BgcTangentPairFP64* tangent);
+
+extern inline void bgc_tangent_pair_set_values_fp32(const float x1, const float x2, BgcTangentPairFP32* tangent);
+extern inline void bgc_tangent_pair_set_values_fp64(const double x1, const double x2, BgcTangentPairFP64* tangent);
+
+extern inline void bgc_tangent_pair_copy_fp32(const BgcTangentPairFP32* from, BgcTangentPairFP32* to);
+extern inline void bgc_tangent_pair_copy_fp64(const BgcTangentPairFP64* from, BgcTangentPairFP64* to);
+
+extern inline void bgc_tangent_pair_swap_fp32(BgcTangentPairFP32* tangent1, BgcTangentPairFP32* tangent2);
+extern inline void bgc_tangent_pair_swap_fp64(BgcTangentPairFP64* tangent1, BgcTangentPairFP64* tangent2);
+
+extern inline void bgc_tangent_pair_set_turn_fp32(const float angle, const BgcAngleUnitEnum unit, BgcTangentPairFP32* tangent);
+extern inline void bgc_tangent_pair_set_turn_fp64(const double angle, const BgcAngleUnitEnum unit, BgcTangentPairFP64* tangent);
+
+extern inline void bgc_tangent_pair_convert_fp64_to_fp32(const BgcTangentPairFP64* from, BgcTangentPairFP32* to);
+extern inline void bgc_tangent_pair_convert_fp32_to_fp64(const BgcTangentPairFP32* from, BgcTangentPairFP64* to);
+
+extern inline void bgc_tangent_pair_invert_fp32(BgcTangentPairFP32* tangent);
+extern inline void bgc_tangent_pair_invert_fp64(BgcTangentPairFP64* tangent);
+
+extern inline void bgc_tangent_pair_set_inverted_fp32(const BgcTangentPairFP32* tangent, BgcTangentPairFP32* result);
+extern inline void bgc_tangent_pair_set_inverted_fp64(const BgcTangentPairFP64* tangent, BgcTangentPairFP64* result);
+
+extern inline void bgc_tangent_pair_make_rotation_matrix_fp32(const BgcTangentPairFP32* tangent, BgcMatrix2x2FP32* matrix);
+extern inline void bgc_tangent_pair_make_rotation_matrix_fp64(const BgcTangentPairFP64* tangent, BgcMatrix2x2FP64* matrix);
+
+extern inline void bgc_tangent_pair_make_reverse_matrix_fp32(const BgcTangentPairFP32* tangent, BgcMatrix2x2FP32* matrix);
+extern inline void bgc_tangent_pair_make_reverse_matrix_fp64(const BgcTangentPairFP64* tangent, BgcMatrix2x2FP64* matrix);
+
+extern inline float bgc_tangent_pair_get_angle_fp32(const BgcTangentPairFP32* tangent, const BgcAngleUnitEnum unit);
+extern inline double bgc_tangent_pair_get_angle_fp64(const BgcTangentPairFP64* tangent, const BgcAngleUnitEnum unit);
+
+extern inline void bgc_tangent_pair_combine_fp32(const BgcTangentPairFP32* tangent1, const BgcTangentPairFP32* tangent2, BgcTangentPairFP32* result);
+extern inline void bgc_tangent_pair_combine_fp64(const BgcTangentPairFP64* tangent1, const BgcTangentPairFP64* tangent2, BgcTangentPairFP64* result);
+
+extern inline void bgc_tangent_pair_turn_vector_fp32(const BgcTangentPairFP32* tangent, const BgcVector2FP32* vector, BgcVector2FP32* result);
+extern inline void bgc_tangent_pair_turn_vector_fp64(const BgcTangentPairFP64* tangent, const BgcVector2FP64* vector, BgcVector2FP64* result);
+
+extern inline void bgc_tangent_pair_turn_vector_back_fp32(const BgcTangentPairFP32* tangent, const BgcVector2FP32* vector, BgcVector2FP32* result);
+extern inline void bgc_tangent_pair_turn_vector_back_fp64(const BgcTangentPairFP64* tangent, const BgcVector2FP64* vector, BgcVector2FP64* result);
+
+extern inline int bgc_tangent_pair_are_close_fp32(const BgcTangentPairFP32* tangent1, const BgcTangentPairFP32* tangent2);
+extern inline int bgc_tangent_pair_are_close_fp64(const BgcTangentPairFP64* tangent1, const BgcTangentPairFP64* tangent2);
+
+void _bgc_tangent_pair_normalize_fp32(const float square_modulus, _BgcTwinTangentPairFP32* twin)
+{
+    // (square_modulus != square_modulus) is true when square_modulus is NaN
+
+    if (square_modulus <= BGC_SQUARE_EPSYLON_FP32 || square_modulus != square_modulus) {
+        twin->cos = 1.0f;
+        twin->sin = 0.0f;
+        return;
+    }
+
+    const float multiplier = sqrtf(1.0f / square_modulus);
+
+    twin->cos *= multiplier;
+    twin->sin *= multiplier;
+}
+
+void _bgc_tangent_pair_normalize_fp64(const double square_modulus, _BgcTwinTangentPairFP64* twin)
+{
+    // (square_modulus != square_modulus) is true when square_modulus is NaN
+
+    if (square_modulus <= BGC_SQUARE_EPSYLON_FP64 || square_modulus != square_modulus) {
+        twin->cos = 1.0;
+        twin->sin = 0.0;
+        return;
+    }
+
+    const double multiplier = sqrt(1.0 / square_modulus);
+
+    twin->cos *= multiplier;
+    twin->sin *= multiplier;
+}
diff --git a/basic-geometry/tangent.h b/basic-geometry/tangent-pair.h
similarity index 52%
rename from basic-geometry/tangent.h
rename to basic-geometry/tangent-pair.h
index 8e26e49..e2fd296 100644
--- a/basic-geometry/tangent.h
+++ b/basic-geometry/tangent-pair.h
@@ -1,5 +1,5 @@
-#ifndef _BGC_TANGENT_H_
-#define _BGC_TANGENT_H_
+#ifndef _bgc_tangent_pair_H_
+#define _bgc_tangent_pair_H_
 
 #include <math.h>
 
@@ -13,41 +13,41 @@
 typedef struct
 {
     const float cos, sin;
-} BgcTangentFP32;
+} BgcTangentPairFP32;
 
 typedef struct
 {
     const double cos, sin;
-} BgcTangentFP64;
+} BgcTangentPairFP64;
 
 // ================= Dark Twins ================= //
 
 typedef struct {
     float cos, sin;
-} _BgcDarkTwinTangentFP32;
+} _BgcTwinTangentPairFP32;
 
 typedef struct {
     double cos, sin;
-} _BgcDarkTwinTangentFP64;
+} _BgcTwinTangentPairFP64;
 
 // ================= Constants ================== //
 
-extern const BgcTangentFP32 BGC_IDLE_TANGENT_FP32;
-extern const BgcTangentFP64 BGC_IDLE_TANGENT_FP64;
+extern const BgcTangentPairFP32 BGC_IDLE_TANGENT_PAIR_FP32;
+extern const BgcTangentPairFP64 BGC_IDLE_TANGENT_PAIR_FP64;
 
 // =================== Reset ==================== //
 
-inline void bgc_tangent_reset_fp32(BgcTangentFP32* tangent)
+inline void bgc_tangent_pair_reset_fp32(BgcTangentPairFP32* tangent)
 {
-    _BgcDarkTwinTangentFP32* twin = (_BgcDarkTwinTangentFP32*)tangent;
+    _BgcTwinTangentPairFP32* twin = (_BgcTwinTangentPairFP32*)tangent;
 
     twin->cos = 1.0f;
     twin->sin = 0.0f;
 }
 
-inline void bgc_tangent_reset_fp64(BgcTangentFP64* tangent)
+inline void bgc_tangent_pair_reset_fp64(BgcTangentPairFP64* tangent)
 {
-    _BgcDarkTwinTangentFP64* twin = (_BgcDarkTwinTangentFP64*)tangent;
+    _BgcTwinTangentPairFP64* twin = (_BgcTwinTangentPairFP64*)tangent;
 
     twin->cos = 1.0;
     twin->sin = 0.0;
@@ -55,51 +55,51 @@ inline void bgc_tangent_reset_fp64(BgcTangentFP64* tangent)
 
 // ==================== Set ===================== //
 
-void _bgc_tangent_normalize_fp32(const float square_modulus, _BgcDarkTwinTangentFP32* twin);
+void _bgc_tangent_pair_normalize_fp32(const float square_modulus, _BgcTwinTangentPairFP32* twin);
 
-void _bgc_tangent_normalize_fp64(const double square_modulus, _BgcDarkTwinTangentFP64* twin);
+void _bgc_tangent_pair_normalize_fp64(const double square_modulus, _BgcTwinTangentPairFP64* twin);
 
-inline void bgc_tangent_set_values_fp32(const float x1, const float x2, BgcTangentFP32* tangent)
+inline void bgc_tangent_pair_set_values_fp32(const float x1, const float x2, BgcTangentPairFP32* tangent)
 {
     const float square_modulus = x1 * x1 + x2 * x2;
 
-    _BgcDarkTwinTangentFP32* twin = (_BgcDarkTwinTangentFP32*)tangent;
+    _BgcTwinTangentPairFP32* twin = (_BgcTwinTangentPairFP32*)tangent;
 
     twin->cos = x1;
     twin->sin = x2;
 
     if (!bgc_is_sqare_value_unit_fp32(square_modulus)) {
-        _bgc_tangent_normalize_fp32(square_modulus, twin);
+        _bgc_tangent_pair_normalize_fp32(square_modulus, twin);
     }
 }
 
-inline void bgc_tangent_set_values_fp64(const double x1, const double x2, BgcTangentFP64* tangent)
+inline void bgc_tangent_pair_set_values_fp64(const double x1, const double x2, BgcTangentPairFP64* tangent)
 {
     const double square_modulus = x1 * x1 + x2 * x2;
 
-    _BgcDarkTwinTangentFP64* twin = (_BgcDarkTwinTangentFP64*)tangent;
+    _BgcTwinTangentPairFP64* twin = (_BgcTwinTangentPairFP64*)tangent;
 
     twin->cos = x1;
     twin->sin = x2;
 
     if (!bgc_is_sqare_value_unit_fp64(square_modulus)) {
-        _bgc_tangent_normalize_fp64(square_modulus, twin);
+        _bgc_tangent_pair_normalize_fp64(square_modulus, twin);
     }
 }
 
 // ==================== Copy ==================== //
 
-inline void bgc_tangent_copy_fp32(const BgcTangentFP32* from, BgcTangentFP32* to)
+inline void bgc_tangent_pair_copy_fp32(const BgcTangentPairFP32* from, BgcTangentPairFP32* to)
 {
-    _BgcDarkTwinTangentFP32* twin = (_BgcDarkTwinTangentFP32*)to;
+    _BgcTwinTangentPairFP32* twin = (_BgcTwinTangentPairFP32*)to;
 
     twin->cos = from->cos;
     twin->sin = from->sin;
 }
 
-inline void bgc_tangent_copy_fp64(const BgcTangentFP64* from, BgcTangentFP64* to)
+inline void bgc_tangent_pair_copy_fp64(const BgcTangentPairFP64* from, BgcTangentPairFP64* to)
 {
-    _BgcDarkTwinTangentFP64* twin = (_BgcDarkTwinTangentFP64*)to;
+    _BgcTwinTangentPairFP64* twin = (_BgcTwinTangentPairFP64*)to;
 
     twin->cos = from->cos;
     twin->sin = from->sin;
@@ -107,33 +107,33 @@ inline void bgc_tangent_copy_fp64(const BgcTangentFP64* from, BgcTangentFP64* to
 
 // ==================== Swap ==================== //
 
-inline void bgc_tangent_swap_fp32(BgcTangentFP32* tangent1, BgcTangentFP32* tangent2)
+inline void bgc_tangent_pair_swap_fp32(BgcTangentPairFP32* tangent1, BgcTangentPairFP32* tangent2)
 {
     const float cos = tangent1->cos;
     const float sin = tangent1->sin;
 
-    _BgcDarkTwinTangentFP32* twin1 = (_BgcDarkTwinTangentFP32*)tangent1;
+    _BgcTwinTangentPairFP32* twin1 = (_BgcTwinTangentPairFP32*)tangent1;
 
     twin1->cos = tangent2->cos;
     twin1->sin = tangent2->sin;
 
-    _BgcDarkTwinTangentFP32* twin2 = (_BgcDarkTwinTangentFP32*)tangent2;
+    _BgcTwinTangentPairFP32* twin2 = (_BgcTwinTangentPairFP32*)tangent2;
 
     twin2->cos = cos;
     twin2->sin = sin;
 }
 
-inline void bgc_tangent_swap_fp64(BgcTangentFP64* tangent1, BgcTangentFP64* tangent2)
+inline void bgc_tangent_pair_swap_fp64(BgcTangentPairFP64* tangent1, BgcTangentPairFP64* tangent2)
 {
     const double cos = tangent1->cos;
     const double sin = tangent1->sin;
 
-    _BgcDarkTwinTangentFP64* twin1 = (_BgcDarkTwinTangentFP64*)tangent1;
+    _BgcTwinTangentPairFP64* twin1 = (_BgcTwinTangentPairFP64*)tangent1;
 
     twin1->cos = tangent2->cos;
     twin1->sin = tangent2->sin;
 
-    _BgcDarkTwinTangentFP64* twin2 = (_BgcDarkTwinTangentFP64*)tangent2;
+    _BgcTwinTangentPairFP64* twin2 = (_BgcTwinTangentPairFP64*)tangent2;
 
     twin2->cos = cos;
     twin2->sin = sin;
@@ -141,21 +141,21 @@ inline void bgc_tangent_swap_fp64(BgcTangentFP64* tangent1, BgcTangentFP64* tang
 
 // ================== Set Turn ================== //
 
-inline void bgc_tangent_set_turn_fp32(const float angle, const BgcAngleUnitEnum unit, BgcTangentFP32* tangent)
+inline void bgc_tangent_pair_set_turn_fp32(const float angle, const BgcAngleUnitEnum unit, BgcTangentPairFP32* tangent)
 {
     const float radians = bgc_angle_to_radians_fp32(angle, unit);
 
-    _BgcDarkTwinTangentFP32* twin = (_BgcDarkTwinTangentFP32*)tangent;
+    _BgcTwinTangentPairFP32* twin = (_BgcTwinTangentPairFP32*)tangent;
 
     twin->cos = cosf(radians);
     twin->sin = sinf(radians);
 }
 
-inline void bgc_tangent_set_turn_fp64(const double angle, const BgcAngleUnitEnum unit, BgcTangentFP64* tangent)
+inline void bgc_tangent_pair_set_turn_fp64(const double angle, const BgcAngleUnitEnum unit, BgcTangentPairFP64* tangent)
 {
     const double radians = bgc_angle_to_radians_fp64(angle, unit);
 
-    _BgcDarkTwinTangentFP64* twin = (_BgcDarkTwinTangentFP64*)tangent;
+    _BgcTwinTangentPairFP64* twin = (_BgcTwinTangentPairFP64*)tangent;
 
     twin->cos = cos(radians);
     twin->sin = sin(radians);
@@ -163,41 +163,41 @@ inline void bgc_tangent_set_turn_fp64(const double angle, const BgcAngleUnitEnum
 
 // ============= Copy to twin type ============== //
 
-inline void bgc_tangent_convert_fp64_to_fp32(const BgcTangentFP64* from, BgcTangentFP32* to)
+inline void bgc_tangent_pair_convert_fp64_to_fp32(const BgcTangentPairFP64* from, BgcTangentPairFP32* to)
 {
-    bgc_tangent_set_values_fp32((float)from->cos, (float)from->sin, to);
+    bgc_tangent_pair_set_values_fp32((float)from->cos, (float)from->sin, to);
 }
 
-inline void bgc_tangent_convert_fp32_to_fp64(const BgcTangentFP32* from, BgcTangentFP64* to)
+inline void bgc_tangent_pair_convert_fp32_to_fp64(const BgcTangentPairFP32* from, BgcTangentPairFP64* to)
 {
-    bgc_tangent_set_values_fp64((double)from->cos, (double)from->sin, to);
+    bgc_tangent_pair_set_values_fp64((double)from->cos, (double)from->sin, to);
 }
 
 // ================= Inversion ================== //
 
-inline void bgc_tangent_invert_fp32(BgcTangentFP32* tangent)
+inline void bgc_tangent_pair_invert_fp32(BgcTangentPairFP32* tangent)
 {
-    ((_BgcDarkTwinTangentFP32*)tangent)->sin = -tangent->sin;
+    ((_BgcTwinTangentPairFP32*)tangent)->sin = -tangent->sin;
 }
 
-inline void bgc_tangent_invert_fp64(BgcTangentFP64* tangent)
+inline void bgc_tangent_pair_invert_fp64(BgcTangentPairFP64* tangent)
 {
-    ((_BgcDarkTwinTangentFP64*)tangent)->sin = -tangent->sin;
+    ((_BgcTwinTangentPairFP64*)tangent)->sin = -tangent->sin;
 }
 
 // ================ Set Inverted ================ //
 
-inline void bgc_tangent_set_inverted_fp32(const BgcTangentFP32* tangent, BgcTangentFP32* result)
+inline void bgc_tangent_pair_set_inverted_fp32(const BgcTangentPairFP32* tangent, BgcTangentPairFP32* result)
 {
-    _BgcDarkTwinTangentFP32* twin = (_BgcDarkTwinTangentFP32*)result;
+    _BgcTwinTangentPairFP32* twin = (_BgcTwinTangentPairFP32*)result;
 
     twin->cos = tangent->cos;
     twin->sin = -tangent->sin;
 }
 
-inline void bgc_tangent_set_inverted_fp64(const BgcTangentFP64* tangent, BgcTangentFP64* result)
+inline void bgc_tangent_pair_set_inverted_fp64(const BgcTangentPairFP64* tangent, BgcTangentPairFP64* result)
 {
-    _BgcDarkTwinTangentFP64* twin = (_BgcDarkTwinTangentFP64*)result;
+    _BgcTwinTangentPairFP64* twin = (_BgcTwinTangentPairFP64*)result;
 
     twin->cos = tangent->cos;
     twin->sin = -tangent->sin;
@@ -205,7 +205,7 @@ inline void bgc_tangent_set_inverted_fp64(const BgcTangentFP64* tangent, BgcTang
 
 // ============== Rotation Matrix =============== //
 
-inline void bgc_tangent_make_rotation_matrix_fp32(const BgcTangentFP32* tangent, BgcMatrix2x2FP32* matrix)
+inline void bgc_tangent_pair_make_rotation_matrix_fp32(const BgcTangentPairFP32* tangent, BgcMatrix2x2FP32* matrix)
 {
     matrix->r1c1 = tangent->cos;
     matrix->r1c2 = -tangent->sin;
@@ -213,7 +213,7 @@ inline void bgc_tangent_make_rotation_matrix_fp32(const BgcTangentFP32* tangent,
     matrix->r2c2 = tangent->cos;
 }
 
-inline void bgc_tangent_make_rotation_matrix_fp64(const BgcTangentFP64* tangent, BgcMatrix2x2FP64* matrix)
+inline void bgc_tangent_pair_make_rotation_matrix_fp64(const BgcTangentPairFP64* tangent, BgcMatrix2x2FP64* matrix)
 {
     matrix->r1c1 = tangent->cos;
     matrix->r1c2 = -tangent->sin;
@@ -223,7 +223,7 @@ inline void bgc_tangent_make_rotation_matrix_fp64(const BgcTangentFP64* tangent,
 
 // ============== Reverse Matrix ================ //
 
-inline void bgc_tangent_make_reverse_matrix_fp32(const BgcTangentFP32* tangent, BgcMatrix2x2FP32* matrix)
+inline void bgc_tangent_pair_make_reverse_matrix_fp32(const BgcTangentPairFP32* tangent, BgcMatrix2x2FP32* matrix)
 {
     matrix->r1c1 = tangent->cos;
     matrix->r1c2 = tangent->sin;
@@ -231,7 +231,7 @@ inline void bgc_tangent_make_reverse_matrix_fp32(const BgcTangentFP32* tangent,
     matrix->r2c2 = tangent->cos;
 }
 
-inline void bgc_tangent_make_reverse_matrix_fp64(const BgcTangentFP64* tangent, BgcMatrix2x2FP64* matrix)
+inline void bgc_tangent_pair_make_reverse_matrix_fp64(const BgcTangentPairFP64* tangent, BgcMatrix2x2FP64* matrix)
 {
     matrix->r1c1 = tangent->cos;
     matrix->r1c2 = tangent->sin;
@@ -241,7 +241,7 @@ inline void bgc_tangent_make_reverse_matrix_fp64(const BgcTangentFP64* tangent,
 
 // =================== Angle =================== //
 
-inline float bgc_tangent_get_angle_fp32(const BgcTangentFP32* tangent, const BgcAngleUnitEnum unit)
+inline float bgc_tangent_pair_get_angle_fp32(const BgcTangentPairFP32* tangent, const BgcAngleUnitEnum unit)
 {
     if (tangent->cos >= 1.0f - BGC_EPSYLON_FP32) {
         return 0.0f;
@@ -262,7 +262,7 @@ inline float bgc_tangent_get_angle_fp32(const BgcTangentFP32* tangent, const Bgc
     return bgc_radians_to_units_fp32(atan2f(tangent->cos, tangent->sin), unit);
 }
 
-inline double bgc_tangent_get_angle_fp64(const BgcTangentFP64* tangent, const BgcAngleUnitEnum unit)
+inline double bgc_tangent_pair_get_angle_fp64(const BgcTangentPairFP64* tangent, const BgcAngleUnitEnum unit)
 {
     if (tangent->cos >= 1.0 - BGC_EPSYLON_FP64) {
         return 0.0;
@@ -285,18 +285,18 @@ inline double bgc_tangent_get_angle_fp64(const BgcTangentFP64* tangent, const Bg
 
 // ================ Combination ================= //
 
-inline void bgc_tangent_combine_fp32(const BgcTangentFP32* tangent1, const BgcTangentFP32* tangent2, BgcTangentFP32* result)
+inline void bgc_tangent_pair_combine_fp32(const BgcTangentPairFP32* tangent1, const BgcTangentPairFP32* tangent2, BgcTangentPairFP32* result)
 {
-    bgc_tangent_set_values_fp32(
+    bgc_tangent_pair_set_values_fp32(
         tangent1->cos * tangent2->cos - tangent1->sin * tangent2->sin,
         tangent1->cos * tangent2->sin + tangent1->sin * tangent2->cos,
         result
     );
 }
 
-inline void bgc_tangent_combine_fp64(const BgcTangentFP64* tangent1, const BgcTangentFP64* tangent2, BgcTangentFP64* result)
+inline void bgc_tangent_pair_combine_fp64(const BgcTangentPairFP64* tangent1, const BgcTangentPairFP64* tangent2, BgcTangentPairFP64* result)
 {
-    bgc_tangent_set_values_fp64(
+    bgc_tangent_pair_set_values_fp64(
         tangent1->cos * tangent2->cos - tangent1->sin * tangent2->sin,
         tangent1->cos * tangent2->sin + tangent1->sin * tangent2->cos,
         result
@@ -305,7 +305,7 @@ inline void bgc_tangent_combine_fp64(const BgcTangentFP64* tangent1, const BgcTa
 
 // ================ Turn Vector ================= //
 
-inline void bgc_tangent_turn_vector_fp32(const BgcTangentFP32* tangent, const BgcVector2FP32* vector, BgcVector2FP32* result)
+inline void bgc_tangent_pair_turn_vector_fp32(const BgcTangentPairFP32* tangent, const BgcVector2FP32* vector, BgcVector2FP32* result)
 {
     const float x1 = tangent->cos * vector->x1 - tangent->sin * vector->x2;
     const float x2 = tangent->sin * vector->x1 + tangent->cos * vector->x2;
@@ -314,7 +314,7 @@ inline void bgc_tangent_turn_vector_fp32(const BgcTangentFP32* tangent, const Bg
     result->x2 = x2;
 }
 
-inline void bgc_tangent_turn_vector_fp64(const BgcTangentFP64* tangent, const BgcVector2FP64* vector, BgcVector2FP64* result)
+inline void bgc_tangent_pair_turn_vector_fp64(const BgcTangentPairFP64* tangent, const BgcVector2FP64* vector, BgcVector2FP64* result)
 {
     const double x1 = tangent->cos * vector->x1 - tangent->sin * vector->x2;
     const double x2 = tangent->sin * vector->x1 + tangent->cos * vector->x2;
@@ -325,7 +325,7 @@ inline void bgc_tangent_turn_vector_fp64(const BgcTangentFP64* tangent, const Bg
 
 // ============ Turn Vector Backward ============ //
 
-inline void bgc_tangent_turn_vector_back_fp32(const BgcTangentFP32* tangent, const BgcVector2FP32* vector, BgcVector2FP32* result)
+inline void bgc_tangent_pair_turn_vector_back_fp32(const BgcTangentPairFP32* tangent, const BgcVector2FP32* vector, BgcVector2FP32* result)
 {
     const float x1 = tangent->sin * vector->x2 + tangent->cos * vector->x1;
     const float x2 = tangent->cos * vector->x2 - tangent->sin * vector->x1;
@@ -334,7 +334,7 @@ inline void bgc_tangent_turn_vector_back_fp32(const BgcTangentFP32* tangent, con
     result->x2 = x2;
 }
 
-inline void bgc_tangent_turn_vector_back_fp64(const BgcTangentFP64* tangent, const BgcVector2FP64* vector, BgcVector2FP64* result)
+inline void bgc_tangent_pair_turn_vector_back_fp64(const BgcTangentPairFP64* tangent, const BgcVector2FP64* vector, BgcVector2FP64* result)
 {
     const double x1 = tangent->sin * vector->x2 + tangent->cos * vector->x1;
     const double x2 = tangent->cos * vector->x2 - tangent->sin * vector->x1;
@@ -345,7 +345,7 @@ inline void bgc_tangent_turn_vector_back_fp64(const BgcTangentFP64* tangent, con
 
 // ================== Are Close ================= //
 
-inline int bgc_tangent_are_close_fp32(const BgcTangentFP32* tangent1, const BgcTangentFP32* tangent2)
+inline int bgc_tangent_pair_are_close_fp32(const BgcTangentPairFP32* tangent1, const BgcTangentPairFP32* tangent2)
 {
     const float d_cos = tangent1->cos - tangent2->cos;
     const float d_sin = tangent1->sin - tangent2->sin;
@@ -353,7 +353,7 @@ inline int bgc_tangent_are_close_fp32(const BgcTangentFP32* tangent1, const BgcT
     return d_cos * d_cos + d_sin * d_sin <= BGC_SQUARE_EPSYLON_FP32;
 }
 
-inline int bgc_tangent_are_close_fp64(const BgcTangentFP64* tangent1, const BgcTangentFP64* tangent2)
+inline int bgc_tangent_pair_are_close_fp64(const BgcTangentPairFP64* tangent1, const BgcTangentPairFP64* tangent2)
 {
     const double d_cos = tangent1->cos - tangent2->cos;
     const double d_sin = tangent1->sin - tangent2->sin;
diff --git a/basic-geometry/tangent.c b/basic-geometry/tangent.c
deleted file mode 100644
index ee74ca1..0000000
--- a/basic-geometry/tangent.c
+++ /dev/null
@@ -1,82 +0,0 @@
-#include "tangent.h"
-
-const BgcTangentFP32 BGC_IDLE_TANGENT_FP32 = { 1.0f, 0.0f };
-
-const BgcTangentFP64 BGC_IDLE_TANGENT_FP64 = { 1.0, 0.0 };
-
-extern inline void bgc_tangent_reset_fp32(BgcTangentFP32* tangent);
-extern inline void bgc_tangent_reset_fp64(BgcTangentFP64* tangent);
-
-extern inline void bgc_tangent_set_values_fp32(const float x1, const float x2, BgcTangentFP32* tangent);
-extern inline void bgc_tangent_set_values_fp64(const double x1, const double x2, BgcTangentFP64* tangent);
-
-extern inline void bgc_tangent_copy_fp32(const BgcTangentFP32* from, BgcTangentFP32* to);
-extern inline void bgc_tangent_copy_fp64(const BgcTangentFP64* from, BgcTangentFP64* to);
-
-extern inline void bgc_tangent_swap_fp32(BgcTangentFP32* tangent1, BgcTangentFP32* tangent2);
-extern inline void bgc_tangent_swap_fp64(BgcTangentFP64* tangent1, BgcTangentFP64* tangent2);
-
-extern inline void bgc_tangent_set_turn_fp32(const float angle, const BgcAngleUnitEnum unit, BgcTangentFP32* tangent);
-extern inline void bgc_tangent_set_turn_fp64(const double angle, const BgcAngleUnitEnum unit, BgcTangentFP64* tangent);
-
-extern inline void bgc_tangent_convert_fp64_to_fp32(const BgcTangentFP64* from, BgcTangentFP32* to);
-extern inline void bgc_tangent_convert_fp32_to_fp64(const BgcTangentFP32* from, BgcTangentFP64* to);
-
-extern inline void bgc_tangent_invert_fp32(BgcTangentFP32* tangent);
-extern inline void bgc_tangent_invert_fp64(BgcTangentFP64* tangent);
-
-extern inline void bgc_tangent_set_inverted_fp32(const BgcTangentFP32* tangent, BgcTangentFP32* result);
-extern inline void bgc_tangent_set_inverted_fp64(const BgcTangentFP64* tangent, BgcTangentFP64* result);
-
-extern inline void bgc_tangent_make_rotation_matrix_fp32(const BgcTangentFP32* tangent, BgcMatrix2x2FP32* matrix);
-extern inline void bgc_tangent_make_rotation_matrix_fp64(const BgcTangentFP64* tangent, BgcMatrix2x2FP64* matrix);
-
-extern inline void bgc_tangent_make_reverse_matrix_fp32(const BgcTangentFP32* tangent, BgcMatrix2x2FP32* matrix);
-extern inline void bgc_tangent_make_reverse_matrix_fp64(const BgcTangentFP64* tangent, BgcMatrix2x2FP64* matrix);
-
-extern inline float bgc_tangent_get_angle_fp32(const BgcTangentFP32* tangent, const BgcAngleUnitEnum unit);
-extern inline double bgc_tangent_get_angle_fp64(const BgcTangentFP64* tangent, const BgcAngleUnitEnum unit);
-
-extern inline void bgc_tangent_combine_fp32(const BgcTangentFP32* tangent1, const BgcTangentFP32* tangent2, BgcTangentFP32* result);
-extern inline void bgc_tangent_combine_fp64(const BgcTangentFP64* tangent1, const BgcTangentFP64* tangent2, BgcTangentFP64* result);
-
-extern inline void bgc_tangent_turn_vector_fp32(const BgcTangentFP32* tangent, const BgcVector2FP32* vector, BgcVector2FP32* result);
-extern inline void bgc_tangent_turn_vector_fp64(const BgcTangentFP64* tangent, const BgcVector2FP64* vector, BgcVector2FP64* result);
-
-extern inline void bgc_tangent_turn_vector_back_fp32(const BgcTangentFP32* tangent, const BgcVector2FP32* vector, BgcVector2FP32* result);
-extern inline void bgc_tangent_turn_vector_back_fp64(const BgcTangentFP64* tangent, const BgcVector2FP64* vector, BgcVector2FP64* result);
-
-extern inline int bgc_tangent_are_close_fp32(const BgcTangentFP32* tangent1, const BgcTangentFP32* tangent2);
-extern inline int bgc_tangent_are_close_fp64(const BgcTangentFP64* tangent1, const BgcTangentFP64* tangent2);
-
-void _bgc_tangent_normalize_fp32(const float square_modulus, _BgcDarkTwinTangentFP32* twin)
-{
-    // (square_modulus != square_modulus) is true when square_modulus is NaN
-
-    if (square_modulus <= BGC_SQUARE_EPSYLON_FP32 || square_modulus != square_modulus) {
-        twin->cos = 1.0f;
-        twin->sin = 0.0f;
-        return;
-    }
-
-    const float multiplier = sqrtf(1.0f / square_modulus);
-
-    twin->cos *= multiplier;
-    twin->sin *= multiplier;
-}
-
-void _bgc_tangent_normalize_fp64(const double square_modulus, _BgcDarkTwinTangentFP64* twin)
-{
-    // (square_modulus != square_modulus) is true when square_modulus is NaN
-
-    if (square_modulus <= BGC_SQUARE_EPSYLON_FP64 || square_modulus != square_modulus) {
-        twin->cos = 1.0;
-        twin->sin = 0.0;
-        return;
-    }
-
-    const double multiplier = sqrt(1.0 / square_modulus);
-
-    twin->cos *= multiplier;
-    twin->sin *= multiplier;
-}
diff --git a/docs/angle-eng.md b/docs/angle-eng.md
index a19e3de..9408f88 100644
--- a/docs/angle-eng.md
+++ b/docs/angle-eng.md
@@ -51,5 +51,4 @@ The ranges of angles are defined with an enumerated type:
 * BGC_ANGLE_RANGE_UNSIGNED is for the unsigned range of values;
 * BGC_ANGLE_RANGE_SIGNED is for the signed range of values.
 
-
 [Documentation](intro-eng.md)
diff --git a/docs/intro-eng.md b/docs/intro-eng.md
index 5ff1441..2f06186 100644
--- a/docs/intro-eng.md
+++ b/docs/intro-eng.md
@@ -51,8 +51,9 @@ the type suffix: bgc_vector3_reset_fp64, bgc_radians_normalize_fp64.
 
 ## Entities
 
+- [Angles](angle-eng.md)
 - [Vectors 2D](vector2-eng.md)
-- Vectors 3D
+- [Vectors 3D](vector3-eng.md)
 - [Quaternions](quaternion-eng.md)
 - [Versors](versor-eng.md)
 
diff --git a/docs/intro-rus.md b/docs/intro-rus.md
index 48b463f..6a6b3f2 100644
--- a/docs/intro-rus.md
+++ b/docs/intro-rus.md
@@ -52,7 +52,8 @@ bgc_vector3_reset_fp64, bgc_radians_normalize_fp64.
 
 ## Сущности
 
+- [Углы](angle-rus.md)
 - [2D векторы](vector2-rus.md)
-- 3D векторы
+- [3D векторы](vector2-rus.md)
 - [Кватернионы](quaternion-rus.md)
 - [Версоры](versor-rus.md)
diff --git a/docs/vector3/copy-eng.md b/docs/vector3/copy-eng.md
index fceb461..1288609 100644
--- a/docs/vector3/copy-eng.md
+++ b/docs/vector3/copy-eng.md
@@ -48,4 +48,4 @@ int main()
 }
 ```
 
-[Documentation](../intro-eng.md) / [2D vectors](../vector3-eng.md)
+[Documentation](../intro-eng.md) / [3D vectors](../vector3-eng.md)
diff --git a/docs/vector3/copy-rus.md b/docs/vector3/copy-rus.md
index c473264..c9891d1 100644
--- a/docs/vector3/copy-rus.md
+++ b/docs/vector3/copy-rus.md
@@ -48,4 +48,4 @@ int main()
 }
 ```
 
-[������������](../intro-rus.md) / [2D �������](../vector3-rus.md)
+[������������](../intro-rus.md) / [3D �������](../vector3-rus.md)
diff --git a/docs/vector3/reset-eng.md b/docs/vector3/reset-eng.md
index dee9b0d..bf9242f 100644
--- a/docs/vector3/reset-eng.md
+++ b/docs/vector3/reset-eng.md
@@ -1,6 +1,6 @@
-# Resetting the state of a 2D vector
+# Resetting the state of a 3D vector
 
-These functions set all coordinates of 2D vectors to 0.
+These functions set all coordinates of 3D vectors to 0.
 
 Function for **BgcVector3FP32**:
 
@@ -42,4 +42,4 @@ int main()
 }
 ```
 
-[Documentation](../intro-eng.md) / [2D vectors](../vector3-eng.md)
+[Documentation](../intro-eng.md) / [3D vectors](../vector3-eng.md)
diff --git a/docs/vector3/reset-rus.md b/docs/vector3/reset-rus.md
index 24c9543..952a267 100644
--- a/docs/vector3/reset-rus.md
+++ b/docs/vector3/reset-rus.md
@@ -42,4 +42,4 @@ int main()
 }
 ```
 
-[������������](../intro-rus.md) / [2D �������](../vector3-rus.md)
+[������������](../intro-rus.md) / [3D �������](../vector3-rus.md)
diff --git a/docs/vector3/set-values-eng.md b/docs/vector3/set-values-eng.md
index 5102ecb..4613173 100644
--- a/docs/vector3/set-values-eng.md
+++ b/docs/vector3/set-values-eng.md
@@ -42,4 +42,4 @@ int main()
 }
 ```
 
-[Documentation](../intro-eng.md) / [2D vectors](../vector3-eng.md)
+[Documentation](../intro-eng.md) / [3D vectors](../vector3-eng.md)
diff --git a/docs/vector3/set-values-rus.md b/docs/vector3/set-values-rus.md
index ae04ec9..eb803f8 100644
--- a/docs/vector3/set-values-rus.md
+++ b/docs/vector3/set-values-rus.md
@@ -42,4 +42,4 @@ int main()
 }
 ```
 
-[������������](../intro-rus.md) / [2D �������](../vector3-rus.md)
+[������������](../intro-rus.md) / [3D �������](../vector3-rus.md)
diff --git a/docs/vector3/swap-eng.md b/docs/vector3/swap-eng.md
index 0adb099..ed60184 100644
--- a/docs/vector3/swap-eng.md
+++ b/docs/vector3/swap-eng.md
@@ -49,4 +49,4 @@ Vector #1: x1 = 10.000000, x2 = -1.000000, x3 = -3.000000
 Vector #2: x1 = -2.000000, x2 = 7.000000, x3 = 5.000000
 ```
 
-[Documentation](../intro-eng.md) / [2D vectors](../vector3-eng.md)
+[Documentation](../intro-eng.md) / [3D vectors](../vector3-eng.md)
diff --git a/docs/vector3/swap-rus.md b/docs/vector3/swap-rus.md
index e458d18..a95c2e4 100644
--- a/docs/vector3/swap-rus.md
+++ b/docs/vector3/swap-rus.md
@@ -49,4 +49,4 @@ Vector #1: x1 = 10.000000, x2 = -1.000000, x3 = -3.000000
 Vector #2: x1 = -2.000000, x2 = 7.000000, x3 = 5.000000
 ```
 
-[Документация](../intro-rus.md) / [2D векторы](../vector3-rus.md)
+[Документация](../intro-rus.md) / [3D векторы](../vector3-rus.md)