title: Android Rotate Matrix
body: <p>I have matrix. This matrix represents array x and y coordinates. For example </p>
  
  <pre><code>float[] src = {7,1,7,2,7,3,7,4};
  </code></pre>
  
  <p>I need to rotate this coordinates to 90 degrees.
  I use  <code>android.graphics.Matrix</code> like this:</p>
  
  <pre><code>    float[] src = {7,1,7,2,7,3,7,4};
      float[] dist = new float[8];
      Matrix matrix = new Matrix();
      matrix.preRotate(90.0f);
      matrix.mapPoints(dist,src);
  </code></pre>
  
  <p>after operation rotate I have array with next values</p>
  
  <pre><code>-1.0    7.0     -2.0    7.0     -3.0    7.0     -4.0    7.0
  </code></pre>
  
  <p>Its is good for area with 360 degrees. 
  And how do rotate in area from 0 to 90? I need set up center of circle in this area but how ?<br>
  Thanks.</p>