Question

已知∠BOC=2∠AOC,OD平分∠AOB,∠AOB=120°,求∠DOC的度数

Answer 1

∠aoc+∠doc=60

1/2∠boc+∠doc=60

1/2(∠bod+∠doc)+∠doc=60

1/2∠bod+3/2∠doc=60

∠bod=1/2∠aob=60

解得∠doc=20