Question

急.如图,点d是△abc中∩abc平分线和∠acb平分线的交点,点e是∠abc外角平分线

Answer 1

连接A,D并延伸到F,则AD为∠A的角平分线

∠D=∠BDF+∠CDF

∠BDF=（∠A+∠ABC)/2

∠CDF=(∠A+∠ACB)/2

则∠D=(∠A+∠A+∠ABC+∠ACB)/2

∠D=90°+∠A/2

∠E=180°-（180°-∠ABC+180°-∠BCA）/2

=（∠ABC+∠BCA）/2

=（180°-∠A）/2