## Calculus (3rd Edition)

$$y = 2 \cos \left(\frac{1}{3} x-\frac{\pi}{4}\right)$$
We are given: $$f(x)=\cos x$$ Then the composite functions is: \begin{align*} y&=2 f\left(\frac{1}{3} x-\frac{\pi}{4}\right)\\ &= 2 \cos \left(\frac{1}{3} x-\frac{\pi}{4}\right) \end{align*} We sketch the result below.