∵BP⊥MC，∴∠PBC+∠PCB=90°，又∵∠PCB+∠PCD=90°，∴∠PBC=∠PCD．∵PD⊥PN，∴∠DPN=90°．∵∠BPC=∠BPN+∠CPN=90°，∠DPN=∠DPC+∠CPN=90°，∴∠BPN=∠DPC．∴△PBN∽△PCD（两角对应相等的两个三角形相似...