You are correct hardstuck! The answer of 2pi^2 is correct, but i have 2 errors in the method. There is an x missing in the square bracket, which should have been x.arcos(x/2) (from part a.). Then error with arcos(1) you mentioned. These errors happen to cancel to give the correct answer.
at 4:42, shouldn't arccos(1) = 0?
thus leaving us with pi(0--pi) = pi(pi) = pi^2, as opposed to 2pi^2?
You are correct hardstuck! The answer of 2pi^2 is correct, but i have 2 errors in the method.
There is an x missing in the square bracket, which should have been x.arcos(x/2) (from part a.).
Then error with arcos(1) you mentioned. These errors happen to cancel to give the correct answer.
@@MathsWithMrLim yep, I see that now. thanks for all the videos you guys do!