docs: public static boolean invert( DMatrix2x2 a , DMatrix2x2 inv ) {
  
          double scale = 1.0/elementMaxAbs(a);
  
          double a11 = a.a11*scale;
          double a12 = a.a12*scale;
          double a21 = a.a21*scale;
          double a22 = a.a22*scale;
  
          double m11 = a22;
          double m12 = -( a21);
          double m21 = -( a12);
          double m22 = a11;
  
          double det = (a11*m11 + a12*m12)/scale;
  
          inv.a11 = m11/det;
          inv.a12 = m21/det;
          inv.a21 = m12/det;
          inv.a22 = m22/det;
  
          return !Double.isNaN(det) && !Double.isInfinite(det);
      }