Vector3D operator +=(Vector3D left, const Vector3D right);
Vector3D operator -=(Vector3D left, const Vector3D right);
Vector3D operator- (Vector3D a, Vector3D b);
Vector3D operator+ (Vector3D a, Vector3D b);
Vector3D operator* (Vector3D a, Vector3D b);
Vector3D operator* (float a, Vector3D b);
Vector3D operator* (Vector3D a, float b);
Vector3D operator/ (Vector3D a, int b);
Matrix3D rotMatrix(Vector3D r);
Matrix3D rotMatrix2(Vector3D r);
float arcctn(float);