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# What is cos^-1(1/2)?

Aug 6, 2016

#### Answer:

$= 60$

#### Explanation:

${\cos}^{-} 1 \left(\frac{1}{2}\right)$
$= 60$

Aug 7, 2016

#### Answer:

$\frac{\pi}{3} , \mathmr{and} \frac{5 \pi}{3}$

#### Explanation:

$\arccos x = \frac{1}{2}$
Trig table of special arcs gives
$\cos x = \frac{1}{2}$ --> $x = \frac{\pi}{3}$
Trig unit circle gives another arc x that has the same cos value -->
$\cos x = \frac{1}{2}$ --> $x = - \frac{\pi}{3}$, or, $x = \frac{5 \pi}{3}$ (co-terminal)
Answers: $\frac{\pi}{3} \mathmr{and} \frac{5 \pi}{3}$