证明:
∵∠CBA=∠DBA,∠ACB=∠ADB,AB=AB
∴△ABC≌∠BAD△ABD (AAS)
∴∠BAC=∠BAD,AC=AD
∵PC⊥AC,PD⊥AD
∴∠ACP=∠ADP=90
∴△APC≌△APD (ASA)
∴PC=PD