$\frac{\cos\left(x\right)}{\sin\left(x\right)}\cdot\frac{\cos\left(x\right)}{\sin\left(x\right)}$

$16+\left[3-9-\left(11-4\right)\right]$

$\int e^{5x}\cdot cos\left(2x\right)dx$

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

$\lim_{x\to0}\frac{cosmx-cosnx}{x^2}$

$12a^3b^2-8ab^3+24a^2b^2$

$\frac{5x^3+x^2-3}{x^2-x+1}$