1、∠1 = ∠4,∠2 = ∠7,∠3 = ∠6,
∠5 = ∠8.
2、80°,50°.
3、30°.
4、50°,25°, 75°.
5、∠ACB = 2∠BAC,提示:由∠ACB =
∠AOB,∠BAC =
∠BOC,∠AOB =
2∠BOC,得∠ACB = 2∠BAC.
6、36°.
7、提示:在PA上截取PD = PC,要说明PA = PB + PC,只要说明DA = PB.由△ABC、△PCD
是等边三角形,可得AC = BC,CD = CP,∠ACD = ∠BCP,于是△ACD ≌ △BCP.DA = PB.