Mathematics matching P 149.3 in the seventh grade of Beijing Normal University. (2)
The vertical line from d to BC is compared with e (this line is the bisector of BC, that is, BD=CD)
According to the equality of sides, the angle of 7515 can be found in the triangle and the length of CD can be found in the triangle ACD. The length of CE found in the triangle CDE is CE=BE.