docs: public static void divide( DMatrix3x3 a , double alpha ) {
          a.a11 /= alpha; a.a12 /= alpha; a.a13 /= alpha;
          a.a21 /= alpha; a.a22 /= alpha; a.a23 /= alpha;
          a.a31 /= alpha; a.a32 /= alpha; a.a33 /= alpha;
      }