$y'+\tan\left(x\right)y=2x\cos\left(x\right)$

$2\sin\left(2\pi\right)$

$120\cdot3$

$\frac{1}{2}ab\:.\:-\frac{1}{2}ab$

$\lim_{r\to3}\left(\frac{r-3}{\sqrt{2r\:+3}-3}\right)$

$tgx\left(1-ctgx\right)+ctgx\left(1-tg^2x\right)+\left(1-cos^2x\right)$

$\frac{x^2-5x\:+\:6}{x^2\:+x\:-\:2}\:+\:\frac{x^2\:+\:x-20\:}{x^2\:-3x\:-\:4}\:$