如图,$\angle A C D$是$\triangle A B C$的外角,$C E$平分$\angle A C D$,若$\angle A = 60 ^ {\circ}$,$\angle B = 40 ^ {\circ}$,则$\angle E C D$等于( )
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∵$\angle A = 60 ^ {\circ}$,$\angle B = 40 ^ {\circ}$,∴$\angle A C D = \angle A + \angle B = 100 ^ {\circ}$,∵$C E$平分$\angle A C D$,∴$\angle E C D = \frac {1} {2} \angle A C D = 50 ^ {\circ}$,故选选项C.