Question

2sina-sin2a/cos2a-1 -ctga​

Answer 1

$frac{2sina-sin2a}{cos2a-1}-ctga=frac{2sina-2, sina, cosa}{(cos^2a-sin^2a)-(sin^2a+cos^2a)}-ctga=frac{2, sinacdot (1-cosa)}{-2sin^2a}-ctga=\\=-frac{1-cosa}{sina}-ctga=-frac{2sin^2frac{a}{2}}{2, sinfrac{a}{2}, cosfrac{a}{2}}-ctga=-frac{sinfrac{a}{2}}{cosfrac{a}{2}}-ctga=-tgfrac{a}{2}-ctga\\ili\\...=-frac{1-cosa}{sina}-frac{cosa}{sina}=frac{-1+cosa-cosa}{sina}=-frac{1}{sina}$

Answer 2

спасибо большое