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.
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Answer:
Given that:-
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.
To find:-
The distance he walked towards the building.
↦ Let the boy initially standing at point Y with inclination 30° and then he approaches the building to the point X with inclination 60°.
From figure,
XY = CD.
⇝ Height of the building = AZ = 30 m.
⇝ AB = AZ – BZ = 30 – 1.5 = 28.5
⇝ Measure of AB is 28.5 m
In right ABD
⇝ tan 30° = AB/BD
⇝ 1/√3 = 28.5/BD
⇝ BD = 28.5√3 m
Again,
In right ΔABC,
⇝ tan 60° = AB/BC
⇝ √3 = 28.5/BC
⇝ BC = 28.5/√3 = 28.5√3/3
Therefore, the length of BC is 28.5√3/3 m
XY = CD = BD – BC = (28.5√3 – 28.5√3/3) = 28.5√3(1-1/3) = 28.5√3 × 2/3 = 57/√3 m.
⋆ Thus, the distance boy walked towards the building is 57/√3 m.
Step-by-step explanation:
Step-by-step explanation:
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