Which of the following equals ?

MATHEMATICS · Single correct · A Level · Mathematics · Trigonometry · Trigonometry

Problem

Which of the following equals sin⁡(α+β)\sin(\alpha+\beta)? (a) cos⁡αcos⁡β−sin⁡αsin⁡β\cos\alpha\cos\beta-\sin\alpha\sin\beta (b) sin⁡αcos⁡β+cos⁡αsin⁡β\sin\alpha\cos\beta+\cos\alpha\sin\beta (c) sin⁡αcos⁡β−cos⁡αsin⁡β\sin\alpha\cos\beta-\cos\alpha\sin\beta (d) cos⁡αcos⁡β+sin⁡αsin⁡β\cos\alpha\cos\beta+\sin\alpha\sin\beta

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