[orth_proj] Suggestions

[longye-tian]

Hi John @jstac

Here are some suggestions after I read the lecture on orthogonal projections.

• For the orthogonal projection theorem, we have a theorem environment, maybe we can put this theorem in this environment. Also apply to other theorems in this lecture and the proof environment as well.
• In this lecture, we refer to the orthogonal projection theorem many times, currently, we call it OPT without link to the therorem, should we set up a clickable link back to this theorem?
• In the first graph of 1.3.2, we have y' and Py' but we don't plot the Py' into blue so it is not really visible from the graph. Maybe we can update the graph to show Py' in blue
• Typo in the proof of first theorem in 1.4.1, "sufficies" to "suffices"
• Currently, we are switching the notation for column of a matrix, we have two notations, one is col_j U, and the other one is col U_j. Maybe we should choose one for consistency.

What do you think about those suggestions?

I'll update them using a PR after your review.

Best,
Longye

[jstac]

Thanks @longye-tian , great suggestions, please go ahead!