Answer
C
Work Step by Step
The standard form of the equation involving a cos function is $y=a\cos bx$. Comparing $y=2\cos x$ to the standard form, we find that $a=2$ and $b=1$.
Since $a=2$, the amplitude of the function is 2. Also, Using the formula $\frac{2\pi}{b}$, we find that the period of $y=2\cos x$ is:
$\frac{2\pi}{b}=\frac{2\pi}{1}=2\pi$
Therefore, we need to find a cos wave whose amplitude is 2 and whose period is $2\pi$. We find that graph of option C is the correct answer in this regard.