$\lim_{x\to\pi\:}\left(\frac{\sec\left(x\right)}{\sin\left(x\right)}\right)$

$csc^2x-1=0$

$\frac{dy}{dx}=\frac{4x}{cosy}$

$\lim_{x\to\frac{\pi}{2}}\left(\frac{1-\sin\left(x\right)}{x-\frac{\pi}{2}}\right)$

$\left(x^2-y^2\right)\frac{dy}{dx}=2xy$

$x^2-x=9$

$\int\left(\frac{3x^4-2x+\sqrt{x}+1}{x^2}\right)dx$