Question

Пожалуйста срочно!!!!! Cos^2t*tg^2t+5cos^2t-1

Answer 1

$cos^2t*tg^2t+5cos^2t-1=cos^2t*frac{sin^2t}{cos^2t}+5cos^2t-1=sin^2t+5cos^2t-1=$
$=sin^2t+cos^2t-1+4cos^2t=1-1+4cos^2t=4cos^2t$