∴∠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