Question

Write the value of cos⁻¹ (cos 6).

Answer 1

We know that
\[\cos^{- 1} \left( \cos{x} \right) = x\]
Now,
\[\cos^{- 1} \left( \cos6 \right) = \cos^{- 1} \left\{ \cos\left( 2\pi - 6 \right) \right\}\]
\[ = 2\pi - 6\]