解答:证明:(1)∠P=180゜-
∠ABC-1 2
∠ACB=180゜-1 2
(180゜-∠A)=90+1 2
∠A1 2
(2)∠P=∠PCD-∠PBD=
∠ACD-1 2
∠ABC=1 2
∠A1 2
(3)∠P=180゜-
∠CBD-1 2
∠BCE1 2
=180゜-
(∠CBD+∠BCE)1 2
=180゜-
(∠A+∠ACB+∠A+∠ABC)1 2
=180゜-
(180゜+∠A)1 2
=90゜-
∠A.1 2