Mathematics

Mathematics

Problem

Which of the following is the correct identity for cos⁡(x−y)\cos(x - y)? a) sin⁡x cos⁡y+cos⁡x sin⁡y\sin x\,\cos y + \cos x\,\sin y b) cos⁡x cos⁡y−sin⁡x sin⁡y\cos x\,\cos y - \sin x\,\sin y c) cos⁡x cos⁡y+sin⁡x sin⁡y\cos x\,\cos y + \sin x\,\sin y d) cos⁡x cos⁡y\cos x\,\cos y

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