$$\frac{x^{-1\:}.\:x^{-2}}{x^3}$$

$$sin^3a-sin^2a-sina+1$$

$$\frac{2}{\cos\left(x\right)+1}-\frac{2}{cos\left(x\right)-1}=4csc^2\left(x\right)$$

$$\int-sen\left(5x\right)\cdot sen\left(cos\left(5x\right)\right)dx$$

$$\lim_{x\to\infty}\left(\frac{2x^3-5x^2+7}{8x^2+3x-1}\right)$$

$$z^4-2z^2-8$$