High school solid geometry

Proof:

Because PA is perpendicular to plane ABC

So PA is perpendicular to BC

And because in triangle ABC

BC is perpendicular to AB

So BC is perpendicular to plane PAB

And because AF belongs to plane PAB

So BC is perpendicular to AF

< p>And because AF is perpendicular to PC

PC intersects BC at point C

So AFAF is perpendicular to plane PBC