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The value of $cos^{-1} (cos 10)$, is |
$4\pi - 10$ $ 10 - 4\pi$ $3\pi - 10$ $ 10 - 3\pi$ |
$4\pi - 10$ |
We know that $cos^{-1} (cos θ)= θ$ if $0 ≤ θ ≤ \pi $. Here, $θ = 10$ radians. Clearly, it does not lie between 0 and $\pi $. However, $(4\pi - 10)$ lies between 0 and $\pi $ such that $cos (4\pi - 10)$ = cos 10. ∴ $cos^{-1}(cos10)= cos^{-1}(cos(4\pi - 10)) = 4 \pi - 10 $ |
