//return the angle between 2 vectors expressed as radians (-PI to PI) float Vector2::AngleBetweenVectors(Vector2 vec_) { Vector2 vec1 = this->GetNormal(); Vector2 vec1_perp = vec1.Rotate90(true); Vector2 vec2 = vec_.GetNormal(); if ( vec1_perp.Dot(vec2) >= 0 ) return acos(vec1.Dot(vec2)); else return -acos(vec1.Dot(vec2)); }