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Question
Express the following as the product of sine and cosine.
sin A + sin 2A
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Solution
sin A + sin 2A = 2 sin`(("A + 2A")/2) cos (("A - 2A")/2)` ...`[∵ sin "C" + sin "D" = sin (("C + D")/2) cos (("C - D")/2)]`
= 2 sin `"3A"/2` cos `"A"/2` ...[∵ cos(-θ) = cos θ]
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