A moving point P is such that the length of the tangent from P to the circle x^2+y^2=16 is equal to the distance of P from point (8,8). Show that the locus of P is the straight line x+y=9.
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2. Let P(x, y) denote a point whose distance to Q(8, 8) equals the tangent segment to the given circle. The you know that the distance d can be calculated by:
3. The distance d, the radius r of the circle and the distance of P to the center of the circle form a right triangle:
4. Plug in r = 4 and dē from the 1st equation into the 2nd equation:
Solve for y.