Hopefully I posted this in the right spot!

If I had an equation of a sine curve, and I wanted to find the cosine curve, would I just subtract $\displaystyle \frac\pi2$ from the horizontal translation value?

Or rather, if I had a set of data, which, when plotted showed sine curve characteristics, but I actually wanted to find the cosine curve of this data; how would I go about doing that? (hopefully that made sense)

Thanks.