If $ - \,\pi \le x \le \pi ,\;\, - \,\pi \le y \le \pi \;\,{\rm{and}}\,\,\cos \,\,x + \cos \,\,y = 2$, then the value of ${\rm{cos}}\left( {x - y} \right)$ is

JEE MATHEMATICS MCQ: TRANSFORMATIONS

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Application +4 | -1

- \,\pi \le x \le \pi ,\;\, - \,\pi \le y \le \pi \;\,\mathrm{and}\,\,\cos \,\,x + \cos \,\,y = 2

, then the value of

\mathrm{cos}\left( {x - y} \right)

View answer and explanation

Correct option: C

Option C (1) is correct because the maximum value of cosine is 1, so both cos(x) and cos(y) must be 1. This implies x = 0 and y = 0, therefore cos(x - y) = cos(0) = 1.

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