Circle and tangent line
Problem 410Published on Saturday, 12th January 2013, 07:00 pm; Solved by 154
Let C be the circle with radius r, x2 + y2 = r2. We choose two points P(a, b) and Q(-a, c) so that the line passing through P and Q is tangent to C.
For example, the quadruplet (r, a, b, c) = (2, 6, 2, -7) satisfies this property.
Let F(R, X) be the number of the integer quadruplets (r, a, b, c) with this property, and with 0 r R and 0 a X.
We can verify that F(1, 5) = 10, F(2, 10) = 52 and F(10, 100) = 3384.
Find F(108, 109) + F(109, 108).