jsl wrote:A circle lies in an X-Y plane, with its center at (1, -3). If the distance between the X-intercepts of the circle is 8 units, what is the area of the circle?
9
16
25
36
64
None of the answer choices above is correct, clearly; there should be a Pi in each, presumably. I know the source of the question, and it's their mistake, not jsl's. In any case, if the x-intercepts are 8 apart, by symmetry they must be at (-3, 0) and (5, 0); that is, the x-co-ordinates of the intercepts must be 4 to the left and right of x=1, the x-co-ordinate of the centre of the circle. This is easier to see if you draw a diagram in the co-ordinate plane. Once you know these points on the circle, you can find that the distance to the centre is 5, so the circle's radius is 5. The area is then Pi*(5)^2 = 25*Pi.
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