(探索题)如图△ABC中,∠ABC,∠ACB的平分线相交于点O. (1)若∠ABC=40°,∠ACB=80°,求∠BOC; (2)你能找出∠A与∠BOC之间的数量关系吗?
问题描述:
(探索题)如图△ABC中,∠ABC,∠ACB的平分线相交于点O.
(1)若∠ABC=40°,∠ACB=80°,求∠BOC;
(2)你能找出∠A与∠BOC之间的数量关系吗?
答
(1)∠BOC=180°-
∠OBC-1 2
∠OCB1 2
=180°-
(∠OBC+∠OCB)1 2
=180°-
(40°+80°)1 2
=180°-
×120°1 2
=120°;
(2)∠BOC=180°-
(∠ABC+∠ACB)1 2
=180°-
(180°-∠A)1 2
=90°+
∠A.1 2