## integration to find marginal pdf

Consider a disc of radius 1 in the plane D in R
D = {(x,y) in R | x^2+y^2 <= 1}
write the marginal pdf of x and y

the joint pdf is 1/Pi for x^2 + y^2 <= 1 right?
to get the pdf of x, I have to integrate the joint pdf wrt y but I can't figure out the limits