//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));
}
