# From the top of a building AB, 60 m high, the angles of depression of the top and bottom of a vertical lamp post CD are observed to be 30° and 60° respectively. Find(i) the horizontal distance between AB and CD.(ii) the height of the lamp post.(iii) the difference between the heights of the building and the lamp post.

In the fig AB is the building of height 60m and CD is the lamp post of height h (m)

(i) In ∆ABC

tan 60° =

√3 =

BC =

On multiplying and dividing by √3, we get

BC = 203

Therefore distance between building

and lamp post is 20√3 m

(ii) In ∆AED

tan 30° =

=

= 20√3

AE = = 20

Therefore height of lamp post is CD = AB-AE 60-20 = 40 m

Therefore height of lamp post is 40 m

(iii) The difference between the height of the building and the lamp post is 60-40 = 20m

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Trick to learn all Trigonometric Formulae28 mins
Champ Quiz | Trigger on Trigonometry47 mins
Fundas of Trigonometry50 mins
Champ Quiz | Trigonometry Important Questions33 mins
NCERT | Trigonometric Identities52 mins
Champ Quiz | NTSE Trigonometry50 mins
Testing the T- Ratios of Specified Angles57 mins
Foundation | Cracking Previous Year IMO QuestionsFREE Class
Basic Concept of Trigonometry43 mins
NCERT | Imp. Qs. on Trigonometry42 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
view all courses