
This is part one of a two-volume book on real analysis and is intended for senior undergraduate students of mathematics who have already been exposed to calculus. The emphasis is on rigour and foundations of analysis. Beginning with the construction of the number systems and set theory, the book discusses the basics of analysis (limits, series, continuity, differentiation, Riemann integration), through to power series, several variable calculus and Fourier analysis, and then finally the Lebesgue integral. These are almost entirely set in the concrete setting of the real line and Euclidean spaces, although there is some material on abstract metric and topological spaces. The book also has appendices on mathematical logic and the decimal system.
I tried once to read Terence Tao's Analysis I [2], it's really good but my main problem was that I wasn't able to know if my proofs are correct when I do an exercise. So maybe the solution is to get a teacher.
[1]: https://en.wikipedia.org/wiki/Principles_of_Mathematical_Ana...
Similarly, Analysis I by Terence Tao has a 'Why do analysis' that has made me actually enjoy analysis.
Try Terence Tao's book Analysis I https://learnaifromscratch.github.io/math.html you pick up the gist of this kind of math doing basic proofs of natural numbers. You see and do enough of these that you will get the first proof here, where the n+1 comes from, and how you can distribute things in/out of any summation notation. The second integral proof from math stackexchange the same applies, remove all the abstract notation and just write down a few series, distribute in the 1/2pi(i). Do this for a few examples and you can probably figure it out yourself.
In the above link there is resources for olympiad and putnam problem solving on YouTube, if you watch some of those you'll see how they train competitors to solve something like this problem. List every tiny idea or strategy you have to prove that binomial identity and pick one that seems the easiest, start there. Fill the variables with corner cases what happens. If it's geometry what happens if you 'stretch and pull' the geometric interpretation by some constant factor. Look at Pascals Array since this is a binomial identity. This is what they do in those seminars if you're interested and it's free for anybody to watch.
When all those proof books throw 'implies' and other logic at you, read through this: https://ncatlab.org/nlab/files/MartinLofOnTheMeaning96.pdf
All those proofs in probability and stats/linear algebra classes will make sense after imo
If you really want to understand these things, start here: https://www.youtube.com/playlist?list=PL5A714C94D40392AB and watch them as you work through Analysis I by Terence Tao, skipping to chapter 2 where he begins from scratch introducing the naturals, integers, etc. Wildberger even shows you how to do algebraic calculus which will help to learn the Tao book when he goes about rigorously introducing calculus defined using limits. For me that helped anyway, seeing Naturals, Ints, Rationals, and Reals constructed from scratch with all their laws/operations defined and proved by Tao then him using analysis to introduce how these tiny changes in calculus work.