Two poles of equal heights are standing opposite to each other
on either side of the road, which is 80 m wide. From a point
between them on the road, the angles of elevation of the top of the
poles are 60⁰ and 30⁰ respectively. Find the height of the poles and
distance of the point from the poles.
Answers
Step-by-step explanation:
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Given
Two poles of equal heights are standing opposite each other on either side of the road, which is 80 m wide. From a point between them on the road, the angles of elevation of the top of the poles are 60° and 30°, respectively. Find the height of the poles and the distances of the point from the poles
Answer
Let AB and CD be the poles of equal height.
O is the point between them from where the height of elevation taken. BD is the distance between the poles.
As per above figure, AB = CD,
OB + OD = 80 m
Now,
In right ΔCDO,
tan 30° = CD/OD
1/√3 = CD/OD
CD = OD/√3 … (1)
Again,
In right ΔABO,
tan 60° = AB/OB
√3 = AB/(80-OD)
AB = √3(80-OD)
AB = CD (Given)
√3(80-OD) = OD/√3 (Using equation (1))
3(80-OD) = OD
240 – 3 OD = OD
4 OD = 240
OD = 60
Putting the value of OD in equation (1)
CD = OD/√3
CD = 60/√3
CD = 20√3 m
Also,
OB + OD = 80 m
⇒ OB = (80-60) m = 20 m
Thus, the height of the poles are 20√3 m and distance from the point of elevation are 20 m and
60 m respectively.