Turn △CPA counterclockwise by 90 to △CP'B to connect P'P, so △CPP' is an isosceles right triangle, and PP'=2√2.

P'B=3 and PB=2, so P' b 2 = P' p 2+Pb 2 = 9. From the inverse theorem value of Pythagorean theorem, it can be known that △BPP' is a right triangle, so ∠ BPC = 90.