THEOREM 1 OF 2: INTEGRATIONS BY SUBSTITUTIONS

[@simongross3122]

Wow, thank you. I don't know why I never learned this at school or university. It's obviously a very useful result.

[@gayansamarasekara]

My pleasure. Indeed it’s a very useful theorem, it has many applications, plenty of substitutions can be eliminated using the theorem. Unfortunately many US calculus textbooks don’t have this theorem, so they usually don’t teach it. I learned it some 25+ years ago while getting ready for an extremely competitive university entrance exam, I found it those days in a book of target problems, under a set of worked examples. Thanks for your comment.

[@felipefred1279]

Thanks for the proofs professor 👏

[@gayansamarasekara]

You are welcome 👏