$$\lim_{x\to0}\left(\frac{3x^{2}}{1-\cos x}\right)$$

$$0\:-\:-1$$

$$\csc\left(\frac{\pi}{2}-x\right)=\sec\left(x\right)$$

$$\int\frac{1}{\sin^2\left(y\right)\cos^4\left(y\right)}dy$$

$$\frac{x^3-9x}{x^3-6x^2+9}$$

$$2x-3x+7$$

$$-\left(+4+18\right)+\left(-13-14\right)$$