Question

已知∠AOB=70°,∠COD=30°,OE,OF分别平分∠AOC,∠BOD

Answer 1

(1)

∠EOF=∠EOC+∠COD+∠DOF=1/2∠AOC+1/2∠BOD+∠COD

=1/2(∠AOB-∠COD)+∠COD

=1/2(∠AOB+∠COD)

=1/2(70°+30°)=50°

（2）

∠EOF=∠EOA+∠AOD+∠DOE=1/2∠AOC+∠AOD+1/2∠DOB

=1/2(∠AOC+2∠AOD+∠DOB)

=1/2(∠AOC+∠AOD +∠AOD+∠DOB)

=1/2(∠COD+∠AOB)

=1/2(30°+70°)=50°