The height of the tower vertically at the orthocenter of the triangle (of sides a, b, c) and subtending ∠A at A is
a
b
c
a+b+c3
If H is the orthocenter and h is the height of the tower then
tanA=hAH and AH=2RcosA
∴ h2RcosA=tanA ⇒ h=2RsinA=a