如图8,在△ABC中,∠ABC,∠ACB的角平分线相交于点Q.①若角ABC=40°,∠ACB=50°,则∠BOC=______②若∠ABC+∠ACB=116°,则∠BOC=——————③若∠A=76°,∠BOC=_______④若∠BOC=120°,则∠A=——————⑤你能找出∠A与∠BOC之间的数量关系吗?

问题描述:

如图8,在△ABC中,∠ABC,∠ACB的角平分线相交于点Q.①若角ABC=40°,∠ACB=50°,则∠BOC=______
②若∠ABC+∠ACB=116°,则∠BOC=——————
③若∠A=76°,∠BOC=_______
④若∠BOC=120°,则∠A=——————
⑤你能找出∠A与∠BOC之间的数量关系吗?

,∠ABC,∠ACB的角平分线相交于点O吧?
1、∠BOC=180°-1/2(∠ABC+∠ACB)
=180°-1/2(40°+50°)
=180°-45°
=135°
2、∠BOC=180°-1/2(∠ABC+∠ACB)
=180°-1/2×116°
=180°-58°
=122°
3、∠BOC=180°-1/2(∠ABC+∠ACB)
=180°-1/2(180°-∠A)
=180°-90°+∠A/2
=90°+∠A/2
=90°+76°/2
=90°+38°
=128°
4、∠BOC=180°-1/2(∠ABC+∠ACB)
=180°-1/2(180°-∠A)
=180°-90°+∠A/2
=90°+∠A/2
∠A/2=120°-90°
∠A/2=30°
∠A=60°
5、∠BOC=90°+∠A/2

,在△ABC中,∠ABC,∠ACB的角平分线相交于点Q.①若角ABC=40°,∠ACB=50°,则∠BOC=_135°_____检举 | 1 分钟前 1556591002 | 浏览次数:4次②若∠ABC+∠ACB=116°,则∠BOC=—143°—————③若∠A=76°,∠BOC=__128...