Thread: Integration by parts.

I almost understand all of this question, except in the last step where we have "128". I will show my work up to that step so you can follow.









I thought that distributing the 8 in step 3 would give us "+32cos...x+c?"

Originally Posted by gammaman

I almost understand all of this question, except in the last step where we have "128". I will show my work up to that step so you can follow.









I thought that distributing the 8 in step 3 would give us "+32cos...x+c?"

It comes from dividing the 32 by the 1/4 in sin(x/4) to give 128

Ok I see it now. The anti-derivative of sin[(1/4)] is -4cos so -4 x -4 = +16
16 x the 8 in front gives us 128.