Because PA⊥ airplane ABC

In this way, the plane PAC⊥ plane ABC and the plane PAB vertical plane ABC are obtained.

The above reasoning is correct, and it is a judgment theorem that the plane is perpendicular to the plane.

* Plane PAB⊥ Plane PBC

Plane PAB∩ Plane PBC=PB

On the Pablo plane, just like AD⊥PB is

Then the AD⊥ aircraft PBC.

∵ BC is on the PBC plane

∴ AD⊥BC ①

It's also PA⊥ airplane ABC.

BC is on the plane ABC.

∴ PA⊥BC ②

∫PA∩AD = A③

To ① ② ③

∴BC⊥ flat pad

∴ BC⊥ Aircraft Company

∫AB in the plane PAB

∴ AB⊥BC