code: public void shear(double proportionX, double proportionY) {
  		Transformation2D temp = new Transformation2D();
  		temp.setShear(proportionX, proportionY);
  		multiply(temp);
  	}
docs: Shears the transformation.
  
  @param proportionX
  The proportion of shearing in x direction.
  @param proportionY
  The proportion of shearing in y direction.