$$\left|-7-13\right|$$

$$\frac{4}{1-\sin\left(x\right)}-\frac{4}{1+\sin\left(x\right)}=8\sec^2\left(x\right)$$

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

$$\frac{dy}{dx}-4y=5sin3x$$

$$\frac{1+\text{senx}}{\cos x}+\frac{\cos x}{1+\text{senx}}=2\sec x$$

$$2x^2y-7xy^2+14y^3$$

$$2,5^{-1,5-3}$$