$\left(4-2-1\right)\left[\left(5\right)\left(5-2-2\right)\right]$

$\int\left(sintcos^2t\right)dt$

$\lim_{x\to-2}\left(\frac{4x^2+18x}{x+2}\right)$

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

$21b+7$

$\frac{7}{x^3}\frac{d}{dx}$

$\sin\left(20\right)=\frac{x}{10}$