Prove that the function given by f(x) = cos x is decreasing in (0… - Vidyadip

Question

Prove that the function given by f(x) = cos x is decreasing in (0, $\pi$).

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Answer

Note that f ′(x) = – sin x
Since for each x ∈ (0, $\pi$), sin x > 0, we have f ′(x) < 0 and so f is decreasing in (0, $\pi$).

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