$\sec\left(x\right)\sin\left(x\right)tg\left(x\right)$

$\frac{d}{dx}\left(-\frac{1}{\arctan\left(e^x\right)}\right)$

$\frac{csc\left(t\right)-sin\left(t\right)}{csc\left(t\right)}=cos^2\left(t\right)$

$y^3=7x+\ln\left(x^2+7\right)$

$-t^2+2t+15$

$-\:x\:+\:2y\:-\:y\:-\:2x\:$

$\frac{cos^2\left(x\right)}{csc^2\left(x\right)-1}=sin^2\left(x\right)$