$\tan^2\left(x\right)\csc\left(x\right)\cos\left(x\right)=1$

$20a-9a$

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

$\frac{dy}{dx}=\frac{5x^3}{4y}$

$\int-\frac{x+1}{x^2+9}dx$

$\int\:x^4\cos\left(2x\right)dx$

$\frac{dy}{dx}=\frac{1}{\left(x+7\right)y^2}$