CPM Homework Help : CCA2 Problem 7-120

Should $y = \sin x$ and $y = \cos x$ both be parent graphs, or is one the parent of the other? Give reasons for your decision.

Hint:

Notice that the sine curve could be shifted horizontally to match the cosine curve, or vice-versa.
What is the horizontal shift?

Answer:

$\text{Since } y = \text{cos }x \text{ is the same as }y = \text{sin }\left(x+\frac{\pi}{2}\right),\text{ only one of these needs to be the parent graph.}$