I have $\displaystyle cos^{-1}(\frac{-1}{2})$ I assume this is the same as $\displaystyle sec(\frac{-1}{2})$ How do I get the "exact value" in radians?
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Originally Posted by Fenixx09 I have $\displaystyle cos^{-1}(\frac{-1}{2})$ I assume this is the same as $\displaystyle sec(\frac{-1}{2})$ How do I get the "exact value" in radians? $\displaystyle f(x) = \cos^{-1}(x)$ is the inverse trig function for cosine, not the reciprocal function. the function's output is an angle. $\displaystyle \cos^{-1}\left(-\frac{1}{2}\right) = \arccos\left(-\frac{1}{2}\right) = \frac{2\pi}{3}$