$7\cos\left(t\right)\tan\left(t\right)$

$\frac{x}{9}\le-2$

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

$\lim_{x\to-1}\left(\frac{3x}{x^2+2x+1}\right)$

$\frac{2}{\:\left(x\left(x+2\right)\left(x^2-1\right)\right)}$

$3x+\frac{1}{4}-x+1\frac{1}{2}and4x+1\frac{3}{4}$

$\sec^20=1+\sin^20\sec^20$