Question

tg2a+1=1/cos2a доказать очееееееень срочно

Answer 1

$tg^2\alpha +1=\frac{1}{cos^2\alpha } \\ \\ tg^2\alpha +1=\frac{sin^2\alpha }{cos^2\alpha } +1=\frac{sin^2\alpha +cos^2\alpha}{cos^2\alpha}= \frac{1}{cos^2\alpha }\\\\\frac{1}{cos^2\alpha }=\frac{1}{cos^2\alpha }$