Question

如图,△ABC中,∠ACB=90°∠ADC=∠ACD,∠BCE=∠BEC,求∠DEC的度数

Answer 1

∠ADC=(180°-∠BAC)/2=90°-∠BAC/2

∠BCE=(180°-∠ABC)/2=90°-∠ABC/2

∠DEC=∠ADC+∠BCE-90°

=90°-∠BAC/2+90°-∠ABC/2-90°

=90°-(∠BAC+∠ABC)/2

=90°-90°/2

=45°