$2tan^2x-tan^4x+3$

$\frac{sin\left(x\right)}{cos\left(x\right)}\:=-\frac{2}{5}$

$y=\frac{3x-x^2}{x+2}$

$\cos2\left|a\right|=1-\sin2\left|a\right|$

$\int_0^{2\pi}\left(sen^2\left(\frac{1}{3}x\right)\right)dx$

$\lim_{x\to3}\:\frac{\left(x-3\right)}{x^3-2}$

$\frac{20x^2y}{36xz}$