Integrals IV is Here!

Oh boy! Integrals IV is now live! This one's got all the juicy integration techniques in it. All of the previous sections have been leading up to this one. This is the meat and potatoes, folks. We've got your u-substitution and your integration by parts, and we've even got your trigonometric substitution and your partial fractions. These are the methods generations of mathematicians have learned and applied time and again for both business and pleasure, time and time again.

I hope that these sections in particular can become great repositories of interesting problems over time. Many problem sets, textbooks, and Q&A sites contain all kinds of interesting examples, and I'd like to include as many of them as I can all in one place. For now, each section has at least 10 problems, but someday I'd like them to be definitive collections.