code: public static void elementDiv( DMatrix2 a , DMatrix2 b) {
          a.a1 /= b.a1;
          a.a2 /= b.a2;
      }
docs: <p>Performs an element by element division operation:<br>
  <br>
  a<sub>i</sub> = a<sub>i</sub> / b<sub>i</sub> <br>
  </p>
  @param a The left vector in the division operation. Modified.
  @param b The right vector in the division operation. Not modified.