设正方形边长为2,则AB=BC=CD=DA=2,AM=MD=DC=NC=1,CM=BN=√5,
易得△NPC∽△NCB,∴PC/CB=NC/NB,PC=CB(NC/NB)=2√5/5,
则PM=CM-PC=3√5/5,
由余弦定理 AP^2=AM^2+PM^2-2*AM*PM*cos∠AMP,
则AP=√(AM^2+PM^2-2*AM*PM*cos∠AMP)=2,
∴PA=AB
设正方形边长为2,则AB=BC=CD=DA=2,AM=MD=DC=NC=1,CM=BN=√5,
易得△NPC∽△NCB,∴PC/CB=NC/NB,PC=CB(NC/NB)=2√5/5,
则PM=CM-PC=3√5/5,
由余弦定理 AP^2=AM^2+PM^2-2*AM*PM*cos∠AMP,
则AP=√(AM^2+PM^2-2*AM*PM*cos∠AMP)=2,
∴PA=AB