We can rewrite this as $\sin(90^{\circ}+20^{\circ}) \cos 20^{\circ}$.
Using the addition formula for sine, we have: $$\sin(90^{\circ}+20^{\circ}) \cos 20^{\circ} = \sin 90^{\circ} \cos 20^{\circ} + \cos 90^{\circ} \sin 20^{\circ}$$
Since $\sin 90^{\circ} = 1$
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