PD AB，PE AC

∴∠ABP=∠DPB,∠ACP=∠EPC

∫BP and CP are equally divided ∠ABC and ∠ACB respectively.

∴∠ABP=∠DBP,∠ACP=∠PCB

∴∠DPB=∠DBP,∠EPC=∠PCB

∴BD=PD,PE=EC

∴c△pde=pd+pe+de=bd+de+ec=bc=5cm