Mark M. answered 02/03/24
Retired Math prof with teaching and tutoring experience in trig.
tana = h/(y-x) and tanb = h/y
So, x(tana)(tanb) = x[h/(y-x)][h/y] = xh2 / [y(y-x)]
and tana - tanb = h/(y-x) - h/y = [hy - h(y-x)] / [y(y-x)] = hx / [y(y-x)]
Therefore, (xtanatanb) / (tana - tanb) = [xh2 / (y(y-x))] ÷ [hx / (y(y-x))]
= [xh2 / (y(y-x))] [ (y(y-x)) / (hx)] = xh2 / (hx) = h