光线在椭圆内的反射

You have shed a ray of ssunhnie into the forum. Thanks!

取自“http://www.onecorner.org/wiki/%E5%85%89%E7%BA%BF%E5%9C%A8%E6%A4%AD%E5%9C%86%E5%86%85%E7%9A%84%E5%8F%8D%E5%B0%84”