Calculate elliptic integrals with W|A?

I need to find a computable form for the height h of a sinusoidal function of length L, whose arc length is required to be 2pi. Therefore I asked Wolfram Alpha for the integral integrate(sqrt(a+(bcos(c*x)))dx, but received a solution I’m having a lot of trouble with.
In particular I do not know how to use the term E(c x|(b^2/(b^2+a)). Of course I’ve tried asking WolframAlpha but there’s not much help forthcoming.
I hope someone can help me onto the right path :slight_smile: