Answer :


In the above figure, let AB be the building such that AB = 60 m. Join A and X. The angles of depression are CAX = 30° and DAX = 60°. Let CD be the lamp post. Join C,D and B,D and C,E. Since AX is parallel to DB, we must have XAC = ACE = 30° and XAD = ADB = 60°. We get two right-angled triangles ∆ABD and ∆CAE. We use trigonometric angle tan in both the triangles with AB as height and DB as base (for ∆ABD) and AE as height and CE as base(for ∆CAE).

We have to find, (i)BD, (ii)CD, and (iii) AB-CD.

From ∆ABD,


DB = CE.

From ∆ACE,




And, the difference between the heights of the building and the lamp post is,

Thus our solutions are,

(i) The horizontal distance between AB and CD = 34.64 m.

(ii) The height of the lamp post = 40 m.

(iii) Difference between the heights of the building and the lamp post = 20 m.

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