Question

△ABC中OB和OC分别是∠ABC、∠ACB的平分线,∠BOC是多少?

Answer 1

(1)∠OBC+∠OCB=1/2(∠ACB+∠ABC)=1/2(180-∠A)=90-1/2∠A

所以∠BOC=180-(90-1/2∠A)=90+1/2∠A

(2)∠ABO+∠ACO=1/2(180-∠B)+1/2(180-∠C)=180-1/2∠B-1/2∠C

=180-1/2(180-∠A)=90+1/2∠A

所以∠BOC=90-1/2∠A

第三个看不懂