$\frac{\tan^2\left(u\right)}{\sec\left(u\right)}=\sec\left(u\right)-\cos\left(u\right)$

$90\left(5\right)^{-1}$

$\left(\frac{3a^{-4}}{b^7}\right)^3$

$a^22ab+b^2$

$\frac{4x^2}{t}-3tx-7$

$\lim_{x\to0}\left(\frac{x-sin\left(x\right)}{1-cos\left(2x\right)}\right)$

$-7\left(5y\:-\:3z\right)\:$