$\lim_{x\to0}\left(\frac{x^2+2x}{\cos\:\left(x+\frac{3\pi\:}{2}\right)}\right)$

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

$\frac{dy}{\cos\left(2x\right)}+\frac{y^2}{dx}=0$

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

$\frac{\sec^2\left(x\right)\tan\left(x\right)}{\cot\left(x\right)\csc^2\left(x\right)}$

$\frac{72}{-2}$

$\frac{2}{1+\sin^2}$