Question
A vertical tower stands on a horizontal plane and is
surmounted by a vertical flag staff of height h. At a point on the plane, the angle of elevation of the bottom of the flag staff is and that of the top of the flag staff is β. Then the height of the tower isSolution
Apply tan
 in ∆BCD Tan
 = x / K k = (x / tan
) ---- (1) apply tanβ in ∆ACD => tanβ = (ĥ+x) / K => K = (h + x) / (tanβ) ----- (2) Example like (1) and (2) => x / tan
 = (h+x) / tanβ => xtanβ = tan
h + xtan
=> xtanβ – xtan
 = h tan
=> x(tanβ – tan
) = h tan
=> x = (h tan2) / (tanβ – tan
)
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