Question

一道正方形题急一个正方形ABCD,在AB边上取一点M,连结MC,MD.求证：∠CMD=45度.

Answer 1

如图：延长DM至F.F∈ABCD的外接圆上.∠DFC＝45°.

∴∠CMD＝45°+∠FCM＞45°,只有M与A或者B重合时,∠CMD＝45°才成立.