- #1

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**[SOLVED] Re: Integral involving square root of e^x**

## Homework Statement

[tex]\int \sqrt{1-e^{-x}}[/tex]

## Homework Equations

Sub rule.

## The Attempt at a Solution

I realised that it's fairly obvious I can use u=e^-x/2 to give [itex]\sqrt {1-u^2}[/itex]

but I'm kind of looking at the answers and I'm not seeing how I can get to them from here?

The answer I have from my maths program looks a bit awkward? Not sure how they got here?

[tex]2(\sqrt{1-e^x})-2\tanh^{-1}(\sqrt{1-e^x})+c[/tex]

Are there any other useful subs anyone can think of, or tips for this one.

Not a homework question as such but I thought this was the best place for it.