1、在△ABC中,P为∠ABC、∠ACB的平分线的交点,求证:∠BPC=90°+1/2∠A证明:∵∠A+∠ABC+∠ACB=180 o∴1/2∠A+1/2∠ABC+1/2∠ACB=90 o∴1/2∠ABC+1/2∠ACB=90 o -1/2∠A∵P为∠ABC、∠ACB的平分线的交点∴∠PBC=1/2∠ABC,∠PCB=1/2∠ACB∴∠BPC=180 o-(∠PBC+∠PCB)=180 o-(1/2∠ABC+1/2∠ACB)=180 o-(90 o -1/2∠A)=90°+1/2∠A2、在△ABC中,P为∠ABC平分线与∠ACB外角的平分线的交点,...