public void AngleTowardTest()
{
var v1 = new Vector3D(10, 0, 0);
var v2 = new Vector3D(2, 5, 0);
var angv1v2_zplus = v1.AngleToward(1e-4, v2, Vector3D.ZAxis);
var angv1v2_zminus = v1.AngleToward(1e-4, v2, -Vector3D.ZAxis);
var angv2v1_zplus = v2.AngleToward(1e-4, v1, Vector3D.ZAxis);
var angv2v1_zminus = v2.AngleToward(1e-4, v1, -Vector3D.ZAxis);
Assert.True(angv1v2_zplus.EqualsTol(rad_tol, angv2v1_zminus));
Assert.True(angv1v2_zplus.EqualsTol(rad_tol, 68.1d.ToRad()));
Assert.True(angv2v1_zplus.EqualsTol(rad_tol, angv1v2_zminus));
Assert.True(angv2v1_zplus.EqualsTol(rad_tol, 291.8d.ToRad()));
}