$\frac{1}{\sin\left(a\right).\cos\left(b\right)}-\frac{\cos\left(b\right)}{\sin\left(a\right)}=\tan\left(c\right)$

$\frac{d}{dx}\left(\sqrt[2]{x}+\sqrt[2]{y}=y+1\right)$

$\frac{n}{-2}>4$

$\lim_{x\to\frac{\pi}{3}}\left(\frac{2\cos^2\left(x\right)-\cos\left(x\right)}{\sin\left(x\right)-\sqrt{3}\cos\left(x\right)}\right)$

$\frac{\left(2tg\alpha\:+cotg\alpha\:\right)}{\left(tg\alpha\:+cotg\alpha\:\right)}=1+sen^2\alpha\:$

$17\cdot18.79$