BC⊥AP
∵PC⊥平面ABC,∴PC⊥BC
∵∠C=90°,∴BC⊥AC
∵PC∩AC于点C，∴BC⊥平面PAC
∴BC⊥AP
BC⊥AP∵PC⊥平面ABC,∴PC⊥BC∵∠C=90°,∴BC⊥AC∵PC∩AC于点C，∴BC⊥平面PAC∴BC⊥AP
