AP ICET 2015 Paper

Question : 123 of 200

Marks: +1, -0

If the angles of elevation of the top of a tower of height 60 m and the top of a flag staff on the tower from a point on the level ground are 30° and 60° respectively, then the length of the flag staff in metres is

Validate

Solution:

AB : Tower
BC : Flagstaff
In ΔBCD,
∠BCD = ∠BDC = 30°
⇒ BC = BD
In ΔDAB,
BD = AB cosec ∠ADB

⇒BD=60\cosec30°=60×2=120m

∴ length of the flagstaff, BC = BD = 120 m
Aliter :

We have,

{BC}/{AB}=({\tanθ_{1}}/{\tanθ_{2}}-1)

⇒{BC}={AB}({\tanθ_{1}}/{\tanθ_{2}}-1)

=60({\tan60°}/{\tan30°}-1)

=60×2=120{m}

Go to Question:

Prev Question

Next Question