Question

如圖，已知∠AOB=50°，OC平分∠AOB.

(1)請(qǐng)?jiān)趫D中∠AOB的外部畫出它的一個(gè)余角∠BOD;
(2)求∠COD的度數(shù)

Answer 1

（1）略
（2）65°

解：（1）（圖略）畫圖正確                     ……3分
（2）∠COD=∠COB＋∠BOD                                           ……4分
=∠AOB＋90°－∠AOB                                   ……6分
=×50°＋90°－50°
=25°＋40°
=65°                                                    ……7分