Integrating by Substitution: Solving Integrals with Square Roots

[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.

 

[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 $$x = 2\tan \theta$$

 

[futb0l]

Right, thanks a lot :D