$$\cot\left(x\right)^2-\cot\left(x\right)+\csc\left(x\right)^2=4$$

$$-35\cdot55$$

$$\frac{dy}{dx}=\frac{y^3}{yx^2-2x^2}$$

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

$$\lim_{x\to0}\frac{\sin^3\left(\sin\left(x\right)\right)}{0}$$

$$\frac{\sin^2\left(t\right)+4\sin^2\left(t\right)+3}{\cos^2\left(t\right)}$$

$$\lim_{x\to0}\left(\frac{\sqrt{x^2+9}}{x}\right)$$