WEBVTT

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Here is the problem: cos(x) equals 2.

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A periodic equation in x.

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Start with the equation.

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Rewrite as f(x) equals 0.

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f repeats every 2pi; it never reaches 0 in one full period. A scan of one whole period (and of [−100, 100]) finds no crossing and no touching point, so it has no real solution.

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So the answer is No real solution.

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Because the function repeats, checking one full period covers every real number.