1. By similar triangles, OA/OB = CX/CB = 3/9
So OA = 4, and AB = 12.6491 by Pythagoras.
2. Let OA = a, OB = b
By similar triangles, (b3)/3 = b/a  (i)
By Pythagoras, a^{2} + b^{2} = 144  (ii)
From (i), 3a + 3b = ab
Squaring, 9a^{2} + 18ab + 9b^{2} = a^{2}b^{2}
From (ii), 9a^{2} + 9b^{2} = 1296
Subtracting, (ab)^{2}  18(ab)  1296 = 0
Solving for (ab) and rejecting negative root,
ab = 46.10795
From (i), a = 3b/(b3)
So 3b^{2}/(b3) = ab = 46.10795
Solving and rejecting smaller root,
b = 11.2827
3. a = 46.10795 / 11.2827 = 4.0866
So DA = 1.0866 
