Question

What is the value of cos [(180 – θ)/2] cos [(180 – 9θ)/2] + sin [(180 – 3θ)/2] sin [(180 – 13θ)/2]?

A sin 2θ sin 4θ
B cos 2θ cos 6θ
C sin 2θ sin 6θ
D cos 2θ cos 4θ
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