如图20,∠ABC＝50º,∠ACB＝60º,∠ABC、∠ACB的平分线交于点O,过点O作EF∥BC交AB于E,交AC于F．求∠BOC的度数

如图20,∠ABC＝50º,∠ACB＝60º,∠ABC、∠ACB的平分线交于点O,过点O作EF∥BC交AB于E,交AC于F．求∠BOC的度数

如图20,∠ABC＝50º,∠ACB＝60º,∠ABC、∠ACB的平分线交于点O,过点O作EF∥BC交AB于E,交AC于F．求∠BOC的度数

如图20,∠ABC＝50º,∠ACB＝60º,∠ABC、∠ACB的平分线交于点O,过点O作EF∥BC交AB于E,交AC于F．求∠BOC的度数
∵∠ABC＝50º,∠ACB＝60º,∠ABC、∠ACB的平分线交于点O
∴∠ABO=∠OBC=1/2∠ABC=25°
∠ACO=∠OCB=1/2∠ACB=30°
∴∠BOC=180°-∠OBC-∠OCB
=180°-25°-30°
=125°