public void Rot01(ref float c, ref float s)
{
Mat3.CalcSymmetricGivensCoefficients(m00, m01, m11, out c, out s);
float cc = c * c;
float ss = s * s;
float mix = 2 * c * s * m01;
SetSymmetric(cc * m00 - mix + ss * m11, 0, c * m02 - s * m12,
ss * m00 + mix + cc * m11, s * m02 + c * m12, m22);
}