Question

The value of \[\cos^{- 1} \left( \cos\frac{5\pi}{3} \right) + \sin^{- 1} \left( \sin\frac{5\pi}{3} \right)\] is

 

Options

• `pi/2`

• `(5pi)/3`

• `(10pi)/3`

• 0

Answer 1

(d) 0

We have
\[\cos^{- 1} \left( \cos\frac{5\pi}{3} \right) + \sin^{- 1} \left( \sin\frac{5\pi}{3} \right) = \cos^{- 1} \left\{ \cos\left( 2\pi - \frac{\pi}{3} \right) \right\} + \sin^{- 1} \left\{ \sin\left( 2\pi - \frac{\pi}{3} \right) \right\}\]
\[ = \cos^{- 1} \left\{ \cos\left( \frac{\pi}{3} \right) \right\} + \sin^{- 1} \left\{ - \sin\left( \frac{\pi}{3} \right) \right\}\]
\[ = \cos^{- 1} \left\{ \cos\left( \frac{\pi}{3} \right) \right\} - \sin^{- 1} \left\{ \sin\left( \frac{\pi}{3} \right) \right\}\]
\[ = \frac{\pi}{3} - \frac{\pi}{3}\]
\[ = 0\]