Question

Value of sin^-1(sin 9pi/7)

Answer 1

Hint:   $\bf \begin{array}{llll} sin^{-1}[sin(whatever)]= whatever\\\\ cos^{-1}[cos(whatever)]= whatever\\\\ tan^{-1}[tan(whatever)]= whatever \end{array}\\\\ ------------------\\\\ \begin{array}{llll} sin[sin^{-1}(whatever)]= whatever\\\\ cos[cos^{-1}(whatever)]= whatever\\\\ tan[tan^{-1}(whatever)]= whatever \end{array}$