解：∵∠ACE=∠A+∠ABC，CP平分∠ACE∴∠PCE＝∠ACE/2＝（∠A+∠ABC）/2∵BP平分∠ABC∴∠PBC＝∠ABC/2∴∠PCE＝∠P+∠PBC＝∠P+∠ABC/2∴(∠A+∠ABC)/2=∠P+∠ABC/2∴∠P=∠A/2＝80/2＝40°
外角关系A=ACE-ABC=2PCE-2PBC=2(PCE-PBC)=2PP=40
