Connecting AC, ∫pa⊥ plane ABCD
∴? The projection of PC on the bottom surface is AC
∴? ∠PCA is the angle formed by PC and plane ABCD.
In the right triangle PAB, AB=6√6, PB=6√ 10.
∴? PA=6*2= 12
In the right triangle PAC,
PA= 12,AC=√2*AB= 12√3
∴? tan∠PCA = PA/AC = 12/( 12√3)=√3/3
∴? ∠PCA=π/6
∴? The angle between PC and plane ABCD is π/6.