I am continuing to learn Lean (see part 1 and part 2). I lost some steam around March-April, but in the last two months I picked it up again. In a way it was a nice spaced repetition for relearning some of the basics. This summary was supposed to be my notes from finishing the rest of Mathematics in Lean and finishing chapters 2 and 3 of exercises from Terence Tao’s Analysis textbook, but also I couldn’t help also comment on the challenges and opportunties I see in doing formal mathematic...