code: public static DMatrix2x2 transpose( DMatrix2x2 input , DMatrix2x2 output ) {
          if( input == null )
              input = new DMatrix2x2();
  
          output.a11 = input.a11;
          output.a12 = input.a21;
          output.a21 = input.a12;
          output.a22 = input.a22;
  
          return output;
      }
docs: <p>
  Transposes matrix 'a' and stores the results in 'b':<br>
  <br>
  b<sub>ij</sub> = a<sub>ji</sub><br>
  where 'b' is the transpose of 'a'.
  </p>
  
  @param input The original matrix.  Not modified.
  @param output Where the transpose is stored. If null a new matrix is created. Modified.
  @return The transposed matrix.