public Matrix3 rotate(float angle){
  if (angle == 0)   return this;
  angle=DEGREE_TO_RAD * angle;
  float cos=(float)Math.cos(angle);
  float sin=(float)Math.sin(angle);
  tmp[0]=cos;
  tmp[1]=sin;
  tmp[2]=0;
  tmp[3]=-sin;
  tmp[4]=cos;
  tmp[5]=0;
  tmp[6]=0;
  tmp[7]=0;
  tmp[8]=1;
  mul(val,tmp);
  return this;
}

public Matrix3 rotate ( float angle ) { if ( angle == 0 ) return this ; angle = DEGREE_TO_RAD * angle ; float cos = ( float ) Math . cos ( angle ) ; float sin = ( float ) Math . sin ( angle ) ; tmp [ 0 ] = cos ; tmp [ 1 ] = sin ; tmp [ 2 ] = 0 ; tmp [ 3 ] = - sin ; tmp [ 4 ] = cos ; tmp [ 5 ] = 0 ; tmp [ 6 ] = 0 ; tmp [ 7 ] = 0 ; tmp [ 8 ] = 1 ; mul ( val , tmp ) ; return this ; }
postmultiplies this matrix with a ( counter - clockwise ) rotation matrix . postmultiplication is also used by opengl es ' gltranslate / glrotate / glscale
