Height and Distance Questions

FACTS  AND  FORMULAE  FOR  HEIGHT  AND  DISTANCE  PROBLEMS

 

 

1.In a right angled OAB, where BOA=θ

 

(i). sinθ =PerpendicularHypotenuse=ABOB

 

(ii). cosθ=BaseHypotenuse=OAOB

 

(iii). tanθ=PerpendicularBase=ABOA

 

(iv). cosecθ =1sinθ=OBAB

 

(v). secθ=1cosθ=OBOA

 

(vi). cotθ=1tanθ=OAAB

 

2. Trigonometrical Identities :

(i)sin2θ+cos2θ=1

(ii). 1+tan2θ=sec2θ

(iii). 1+cot2θ=cosec2θ

 

3. Values of T-ratios :

θ0o30o45o60o90osin θ01212321cos θ13212120tan θ01313Not defined

 

4. Angle of Elevation:

Suppose a man from a point O looks up at an object P, placed above the level of his eye. Then, the angle which the line of sight makes with the horizontal through O, is called the angle of elevation of P as seen from O.

Therefore, Angle of elevation of P from O is =AOP

 

5. Angle of Depression :

Suppose a man from a point O looks down at an object P, placed below the level of his eye, then the angle which the line of sight makes with the horizontal through O, is called the angle of depression of P as seen from O.

Q:

Two ships are sailing in the sea on the two sides of a light house. The angle of elevation of the top of the light house as observed from the two ships are 30° and 45° respectively. If the light house is 100m high, the distance between the two ships is :(take √3=1.73)

A) 173m B) 200m
C) 273m D) 300m
 
Answer & Explanation Answer: C) 273m

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Q:

A telegraph post is bent at a point above the ground. Its top just touches the ground at a distance of 8√3 m from its foot and makes an angle of 30° with the horizontal. The height (in metre) of the post is

A) 12 B) 16
C) 18 D) 24
 
Answer & Explanation Answer: D) 24

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Q:

The angle of elevation of an aeroplane as observed from a point 30 m above the transparent water-surface of a lake is 30° and the angle of depression of the image of the aeroplane in the water of the lake is 60°. The height of the aeroplane from the water-surface of the lake is

A) 60 m B) 45 m
C) 50 m D) 75 m
 
Answer & Explanation Answer: A) 60 m

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Q:

Two poles of the height 15 m and 20 m stand vertically upright on a plane ground. If the distance between their feet is 12 m, find the distance between their tops.

A) 11 m B) 12 m
C) 13 m D) 14 m
 
Answer & Explanation Answer: C) 13 m

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Q:

A pilot in an aeroplane at an altitude of 200 m observes two points lying on either side of a river. If the angles of depression of the two points be 45° and 60°, then the width of the river is

A) (200 + 200/√3) m B) (200 - 200/√3) m
C) 400 √3 m D) (400/√3) m
 
Answer & Explanation Answer: B) (200 - 200/√3) m

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Q:

The length of shadow of a tower is √3 times that of its length. The angle of elevation of the sun is

A) 45° B) 30°
C) 60° D) none
 
Answer & Explanation Answer: B) 30°

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Q:

From the top of a platform, the angle of elevation of a tower was 30 deg. The tower was 45 mts high and the horizontal distance between the platform and the tower was 40√3 m. What was the height of the platform?

A) 40 m B) 5 m
C) 45√3 m D) 20√3 m
 
Answer & Explanation Answer: B) 5 m

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Q:

The angle of elevation of an aeroplane from a point on the ground is 60 deg. After flying for 30 seconds, the angle of elevation changes to 30 deg. If the aeroplane is flying at a height of 4500 m, then what is the speed (in m/s) of aeroplane?

A) 50√3 B) 100√3
C) 200√3 D) 300√3
 
Answer & Explanation Answer: B) 100√3

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