Question

Помогите) 10 класс,Алгебра

Answer 1

$\frac{1-cos^2t}{1-sin^2t}+tgtctgt= \frac{1}{cos^2t} \\\ \frac{sin^2t}{cos^2t}+1= \frac{1}{cos^2t} \\\ \frac{sin^2t+cos^2t}{cos^2t}= \frac{1}{cos^2t} \\\ \frac{1}{cos^2t} =\frac{1}{cos^2t}$