∴∠C+∠MPL=∠CMP+∠CLP= 180 degree.

∴ Quadrilateral CMPL is a rectangle

∴PM=PL

∠∠PAC =∠PBC∠AMP =∠BLP。

∴△AMP≌△BLP

∴AM=BL,AP=BP

∴∠PAB=∠PBA，

∠∠MAD =∠PAC+∠PAB，∠LBD=∠PBC+∠PBA

∴∠MAD=∠LBD

∴△MAD≌△LBD

∴DM=DL