An ellipse whose axes are parallel to the coordinate axes is tangent to the x-axis at (4, 0) and tangent to the y-axis at (0, 1). Find the distance between the foci of the ellipse.
The center of the ellipse is ( 4, 1)
The major axis lies along x and the minor axis lies along y
The equation of the ellipse is
(x - 4)^2 / 16 + (y - 1)^2 / 1 = 1
c = sqrt (4^2 - 1) = sqrt (15)
And the distance between the foci = 2c = 2sqrt (15)