Which of the following equalities holds true for every real number ?

MATHEMATICS · Single correct · CBSE · Mathematics · Introduction to Trigonometry · Introduction to Trigonometry

Problem

Which of the following equalities holds true for every real number xx? (a) tan⁡2x+1=sec⁡x\tan^{2}x+1=\sec x (b) sin⁡x+cos⁡x=1\sin x+\cos x=1 (c) sin⁡2x+cos⁡2x=1\sin^{2}x+\cos^{2}x=1 (d) sin⁡2x−cos⁡2x=1\sin^{2}x-\cos^{2}x=1

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