Question

Нужно сократить
(tga+ctga)*sin^2a

Answer 1

$(tg alpha +ctg alpha )* sin^{2} alpha =( frac{sin alpha ^{(sin alpha } }{cos alpha }+ frac{ cos alpha ^{(cos alpha } }{sin alpha } )* sin^{2} alpha =$
$= frac{ sin^{2} alpha + cos^{2} alpha }{sin alpha *cos alpha } * sin^{2} alpha = frac{1}{cos pi } *sin alpha =tg alpha$