How do you calculate the ${cos}^{- 1} (- \frac{\sqrt{2}}{2})$ $cos^-1 (-sqrt2/2)$ ?

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Answer 1 · 2015-12-07T03:34:34

Evaluate ${cos}^{- 1} (- \frac{\sqrt{2}}{2})$ $cos^-1 (-sqrt2/2)$

Ans: $\pm \frac{3 π}{4}$ $+- (3pi)/4$

Trig table of special arcs and unit circle -->
$cos x = - \frac{\sqrt{2}}{2}$ $cos x = -sqrt2/2$ --> arc $x = \pm \frac{3 π}{4}$ $x = +-(3pi)/4$

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