The graph of $y = \cos x$ is the graph of $y = \sin x$ shifted to the left by $\frac{\pi}{2}$ units. This is because the cosine function is essentially the sine function with a phase shift of $\frac{\pi}{2}$ to the left. Mathematically, this can be expressed as:

$\cos x = \sin \left( x + \frac{\pi}{2} \right)$

Would you like more details on phase shifts and transformations of trigonometric functions?

Here are 5 questions you might consider next:

1. How do you graph transformations of the sine and cosine functions?
2. What is the phase shift of the function $y = \sin(x - \frac{\pi}{4})$?
3. Can you explain amplitude and period changes in trigonometric functions?
4. How do you find the equation of a sine function given its graph?
5. What are the key differences between sine and cosine functions?

Tip: When working with trigonometric functions, always pay attention to phase shifts, which are horizontal translations, and how they affect the graph of the function.