Find the principal value of each of the following :\(\cos^{-1}\left(\c

1.	Find the principal value of each of the following :\(\cos^{-1}\left(\cos\frac{13\pi}{6}\right)\)
Answer» \(\cos^{-1}\left(\cos\frac{13\pi}{6}\right)\)\(=\cos^{-1}\left(\cos\left(2\pi+\frac{\pi}{6}\right)\right)\) [ Formula: cos (2π + x) = cos x , cos is positive in the first quadrant. ] \(\cos^{-1}\left(\cos\frac{\pi}{6}\right)\) [Formula: cos ^-1(cos x) = x] \(=\frac{\pi}{6}\)

Find the principal value of each of the following :\(\cos^{-1}\left(\cos\frac{13\pi}{6}\right)\)

Answer»

\(\cos^{-1}\left(\cos\frac{13\pi}{6}\right)\)\(=\cos^{-1}\left(\cos\left(2\pi+\frac{\pi}{6}\right)\right)\)

[ Formula: cos (2π + x) = cos x , cos is positive in the first quadrant. ]

\(\cos^{-1}\left(\cos\frac{\pi}{6}\right)\) [Formula: cos ^-1(cos x) = x]

\(=\frac{\pi}{6}\)