Even in a 12-hour paper my blood would run cold if I came across something like that.
Failing an error on the 4th derivative, may I hope to have made a mistake about the method we use? (ie. maximise the xi term to give a "worst case error"
You must keep adding the terms together at the end of each derivative calculation. It helps. I ended up getting -119e2xsin(3x) - 120e2xcos(3x). [edit: lecturer is in agreement up to here and so my calculations further should be fine]
My end result for that question was 96 panels after some rounding and ensuring an even value.
Thanks. Yes that makes sense. I think some of the terms might even vanish. Again, I suppose if it eats time, it also spits out marks in return, so it's not really something for me to be whingeing about.