Let us consider a triangle where AB to be the flagstaff of 10 m and BC to be of 20 m as the distance between the tower and the flag. Considering ABC and ADE as triangle AB = 10 = CE BC = 20 = AE Calculating the values of ABC tan x = AB/BC tan x = 10/20 10/tan x = 20..............(1) Calculating the values of ADE tan(90-x) = DE/AE cot x = DE/20 DE/cot x = 20 .............(2) Solving equations 1 & 2 10/tan x = DE/cot x DE = 40 Hence the total height of the tower is DE+CE = 40+10= 50 m.