Question

Write the value of \[\cos^{- 1} \left( \cos\frac{14\pi}{3} \right)\]

Answer 1

\[\cos^{- 1} \left( \cos\frac{14\pi}{3} \right) = \cos^{- 1} \left[ \cos\left( 4\pi + \frac{2\pi}{3} \right) \right]\]
\[ = \cos^{- 1} \left( \cos\frac{2\pi}{3} \right)\]
\[ = \frac{2\pi}{3}\]