Adding lines to the finale of the senior high school entrance examination is generally to add height. If you look at a special figure, such as the midpoint of a right triangle with a hypotenuse, add a center line to the hypotenuse.

The most important thing about the moving point problem is to see clearly the moving range of the moving point. If it is a moving point on a ray or a straight line, we should also consider the movement of the moving point outside the closed figure, and remember to discuss it in categories.