Answer
$0$
Work Step by Step
We know that $\sin{(\theta)}=\cos{(90^{\circ}-\theta)}$, hence $\sin{(40^{\circ})}-\cos{(50^{\circ})}=\cos{(90^{\circ}-40^{\circ})}-\cos{(50^{\circ})}=\cos{(50^{\circ})}-\cos{(50^{\circ})}=0.$
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