Mathematics

Mathematics

Problem

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

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