Question

cos^-1(cos\(\frac { 13π }{ 6 }\))
 

Answer 1

cos^-1(cos\(\frac { 13π }{ 6 }\)) = cos^-1cos(2π + \(\frac { π }{ 6 }\) = cos^-1cos\(\frac { π }{ 6 }\)) = \(\frac { π }{ 6 }\)