I need to show that using trig substitution.

I've tried the following:

but

Where am I going wrong?

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- March 8th 2009, 12:14 AMmadmartiganoIntegration by trig substitution
I need to show that using trig substitution.

I've tried the following:

but

Where am I going wrong? - March 8th 2009, 12:21 AMJeWiSh
- March 8th 2009, 12:33 AMmadmartigano
The problem is strange but necessary. I would prefer to use u=x^2+4 and be done with it, but unfortunately I can't. I've been working at this problem for an hour; I don't know where I'm erring.

- March 8th 2009, 12:40 AMOpalg
You're not going wrong. Use properties of logarithms to see that , which differs from the given answer only by a constant of integration.

I have to agree with**JeWiSh**that this is a really daft way to calculate this integral. Much better would be to make the substitution , leading immediately to the answer . - March 8th 2009, 12:52 AMmadmartigano
Ahhh. I separated the log the same as you, but I disregarded the answer because of the additional ln 2. Thank you for clarifying things.