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# Give the cdf and pdf given that we select a point uniformly on an annulus

Select uniformly a point from the annulus $$\{(x,y):1\leq x^2+y^2\leq 4\}$$. Let R be the distance to $$(0,0)$$. Give the cdf and pdf of R.

I know that the sample space of choosing a point would be the area of the annulus ($$3\pi$$) and I know the method of getting the pdf from the cdf or vice versa. I’m just not sure how to start; How would I represent the distance R from the point (x,y) and would this be the cdf or pdf?