This topic examines the properties of square, pythagorean theorem and isosceles triangle, and draws the conclusion that the key to solving the problem is that the corresponding sides are equal by using the properties of axial symmetry. Answer/exercise/math /798053/? If lal is helpful, I hope to adopt it ~ I believe you will understand after reading the answer.

Make a straight line AP on the outside of the square ABCD, and the symmetry point of point B about the straight line AP is E, connecting BE and de, where DE intersects the straight line AP at point F. Look at the red font, which is very helpful. Come on ~