# Homework Help: Question about Legendre elliptic integrals

1. Mar 2, 2017

### mercenarycor

1. The problem statement, all variables and given/known data
J(a, b, c;y)=∫aydx/√((x-a)(x-b)(x-c)), let a<b<c

2. Relevant equations
f(θ, k)=∫0θdx/√(1-k2sin2(x)), k≤1

3. The attempt at a solution
This is an example from my study material, and I don't understand the first step they do.
Let x=a+(b-a)t, dx=(b-a)dt
Wait...what? Why? How did they come to that decision. I hope there's a logical reason, otherwise how can I apply this to my other problems? I keep running into "make an educated guess." Is this another guess?

2. Mar 4, 2017

### John Park

I suggest you show a bit of unquestioning blind faith and try it.

3. Mar 21, 2017

### mercenarycor

And that is how we discovered the new world!

4. Mar 21, 2017

### John Park

No shipwrecks or monstrous squid, I take it?

5. Mar 21, 2017

### mercenarycor

Devoured by the Kraken, I'm afraid. Ended up dropping the course, going to spend the summer with Schaum's trying to build a better foundation for the math I need.