integral btwn 1 and 2 of 1/sqrt{4-x^2} dx

Having a tough time with this one. I tried making \sqrt{4-x^2} into the formula of a circle, but then wasnt sure what to do with the area of 1 quadrent of a circle between 1 and 2. Also tried and failed with 1/\sqrt{4(1-x^2/4)}= 1/4cos(\theta).

can anyone give some insight?