Provide proper documentation for non-mutating functions

[jon-tow]

A quick clean up to help with #160 to avoid wasting time.

[Shashi456]

I think this still needs to be addressed.
Also there are a variety of functions at large which need some sorta explanation and clean-up in a similar fashion.

[jon-tow]

Ah sorry, I thought I'd save you some time with this. Should I close this?

[Shashi456]

@jon-tow no, this is good work. We can discuss some things about the variety of functions in Math.swift, this does save time.

[googlebot]

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[googlebot]

So there's good news and bad news.

👍 The good news is that everyone that needs to sign a CLA (the pull request submitter and all commit authors) have done so. Everything is all good there.

😕 The bad news is that it appears that one or more commits were authored or co-authored by someone other than the pull request submitter. We need to confirm that all authors are ok with their commits being contributed to this project. Please have them confirm that here in the pull request.

Note to project maintainer: This is a terminal state, meaning the cla/google commit status will not change from this state. It's up to you to confirm consent of all the commit author(s), set the cla label to yes (if enabled on your project), and then merge this pull request when appropriate.

ℹ️ Googlers: Go here for more info.

[rxwei]

Thanks!

[jon-tow]

I confirm the co-authoring! (Not sure how to handle the googlebot co-authoring check.)