@Riemannintegral this is impressive. Can I ask how you intuit part (iii). Is it practice / intuition around the previously mentioned u = pi - x substitution / something else
I just used the previous substitution. I also tried reversing a quotient rule derivative but that didn’t arrive at an answer. I’ve been doing step questions for 2 years now and typically make progress by following hints from previous parts of the question.
Very helpful, thank you