Sin^2x=1 , cos ^2x=1 tg^2x=1 

[latex]1)sin ^{2} x=1 => sinx=+-1 => x=frac{ pi }{2}+ pi n;[/latex] [latex]2) cos^{2}x=1 => cosx=+-1 => x=pi n;[/latex] [latex]3) tg^{2}x=1 => tgx=+-1 => x=frac{ pi }{4}+ frac{ pi }{2} n;[/latex]