Applications of Trigonometry Heights and Distances Chapter 9 Exercise 9.1 Question 6
6. A 1.5 m tall boy is standing at some distance from a 30 m tall building. The angle of elevation from his eyes to the top of the building increases from 30
to 60
as he walks towards the building. Find the distance he walked towards the building.
Solution:
We are given the height of tower (AF) = 30 m
The height of boy (BD) = 1.5 m
Therefore, AC = AF – BD = 30 -1.5 = 28.5 m
We want to find distance he walked towards the tower which is BG.
In
, we have
m
In
, we have
m
BG=BC-GC
m
Therefore, he walks
m towards the tower.
Aravind says
how we should find what angle sin,cos,tan or others should come?????
Jashan says
As far as I understand your question, are you trying to ask how do we get to know that we are supposed to use sin, cos or tan. It all depends on which sides are given to us.
Thanks