# Integration by Substituion

1. Oct 12, 2006

### futb0l

Can anyone help me with the following integrals (integrate by substitution)?

$$\int{\frac{dx}{\sqrt{x^2 - 4}}}$$

$$\int{\frac{dx}{\sqrt{x^2 + 4}}}$$

I have no idea whatsoever on how to do it.

2. Oct 12, 2006

### courtrigrad

$$\int{\frac{dx}{\sqrt{x^2 - 4}}}$$. Use the substitution $$x = 2\sec \theta$$

$$\int{\frac{dx}{\sqrt{x^2 + 4}}}$$ Use the substitution $$x = 2\tan \theta$$

3. Oct 12, 2006

### futb0l

Right, thanks a lot :D

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