Got answer, substitute from two lines up. Thanks all.
I do Calculas of Variations, and have an exam in around nine hours, so would appreciate help before then. After is good too thhough.
I got a solution, but it has a bit I don't understand, was hoping you guys could help.
My problem is:
Find extremal of J(y)= ,subject to .
Solution that I have gotten is:
C arbitary constant
Put u in, integrate, change the result around a small bit and you get
D arbitary constant
inset bound conditions, you get
Diffretiate with respect to x;
Then (And herin lies the problem), I get
How does he change into
Thanks in advance.