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

$7mn\left(21x-1\right)$

$25y^6z^4-36m^8$

$7\left(3+5\right)$

$\left(\frac{2}{5}x-2\right)^3$

$\left(6a^x+\:4b^y\right)\:\left(6a^x\:-\:4b^y\right)\:$

$\frac{dy}{dx}e^{-5x}+3=0$