# Problem of the Week

## Updated at Feb 8, 2016 8:57 AM

How can we find the derivative of $$7x-\tan{x}$$?

Below is the solution.

$\frac{d}{dx} 7x-\tan{x}$

 1 Use Sum Rule: $$\frac{d}{dx} f(x)+g(x)=(\frac{d}{dx} f(x))+(\frac{d}{dx} g(x))$$.$(\frac{d}{dx} 7x)-(\frac{d}{dx} \tan{x})$2 Use Power Rule: $$\frac{d}{dx} {x}^{n}=n{x}^{n-1}$$.$7-(\frac{d}{dx} \tan{x})$3 Use Trigonometric Differentiation: the derivative of $$\tan{x}$$ is $$\sec^{2}x$$.$7-\sec^{2}x$Done7-sec(x)^2