Question

помогите пожалуйста, четные

Answer 1

423.
2)
$cos^2 alpha tg^2(- alpha )-1=cos^2 alpha *tg^2 alpha -1= \ \ =cos^2 alpha * frac{sin^2 alpha }{cos^2 alpha }-1=sin^2 alpha -1=-(1-sin^2 alpha )=-cos^ 2alpha$

4)
$frac{1-tg(-x)}{sinx+cos(-x)}= frac{1+tgx}{sinx+cosx}= frac{1+ frac{sinx}{cosx} }{sinx+cosx}= \ \ = frac{cosx+sinx}{cosx(sinx+cosx)}= frac{1}{cosx}$

6)
$tg(-u)ctgu+sin^2u=-tgu*ctgu+sin^2u=-1+sin^2u= \ \ =-(1-sin^2u)=-cos^2u$

8)
$frac{tg(-x)+1}{1-ctgx}= frac{-tgx+1}{1- frac{cosx}{sinx} }= frac{1- frac{sinx}{cosx} }{ frac{sinx-cosx}{sinx} }= \ \ = frac{cosx-sinx}{cosx}* frac{sinx}{-(cosx-sinx)}=-tgx$