∠P=180°-1/2∠B-∠BAP
=180°-1/2∠B-(180°-1/2∠A邻补角)
=180°-1/2∠B-(180°-1/2(180°-∠A))
=180°-1/2∠B-(180°-90°+1/2∠A)
=180°-1/2∠B-90°-1/2∠A
=90°-1/2(∠B+∠A)
=90°-45°
=45°
∠P=180°-1/2∠B-∠BAP
=180°-1/2∠B-(180°-1/2∠A邻补角)
=180°-1/2∠B-(180°-1/2(180°-∠A))
=180°-1/2∠B-(180°-90°+1/2∠A)
=180°-1/2∠B-90°-1/2∠A
=90°-1/2(∠B+∠A)
=90°-45°
=45°