A flag is standing vertically on a tower of height b. On a point at a distance a from the foot of the tower, the flag and the tower subtend equal angles. The height of the flag is
(a) b. \(\frac{a^2+b^2}{a^2-b^2}\)
(b) a. \(\frac{a^2-b^2}{a^2+b^2}\)
(c) a. \(\frac{a^2+b^2}{a^2-b^2}\)
(d) b. \(\frac{a^2-b^2}{a^2+b^2}\)