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Chapter 11 · Class 10 Mathematics

Some Applications of Trigonometry — Important Questions

25 questions With answers CBSE format

SUMMARY: This chapter focuses on the practical applications of trigonometry in real-life situations, particularly in calculating heights and distances.
KEY TOPICS: angle of elevation, angle of depression, line of sight, trigonometric ratios, height and distance problems, real-life applications, solving right triangles, word problems, practical examples, surveying techniques.

Q1 1 Mark

What is the angle of elevation if a person is looking at the top of a 30-meter tall building from a distance of 40 meters?

A30°
B36.87°
C45°
D53.13°
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Correct answer: Option 2 — 36.87°
Q2 1 Mark

If the angle of depression from the top of a tower to a point on the ground is 60°, and the height of the tower is 50 meters, what is the distance from the base of the tower to the point on the ground?

A25√3 meters
B50√3 meters
C100 meters
D50 meters
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Correct answer: Option 1 — 25√3 meters
Q3 1 Mark

In a right triangle, if one angle is 30° and the hypotenuse is 10 cm, what is the length of the side opposite to the 30° angle?

A5 cm
B10 cm
C8.66 cm
D7.5 cm
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Correct answer: Option 1 — 5 cm
Q4 1 Mark

A ladder leans against a wall making an angle of 75° with the ground. If the foot of the ladder is 2 meters away from the wall, how high does the ladder reach on the wall?

A1.93 meters
B2.00 meters
C2.50 meters
D3.87 meters
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Correct answer: Option 1 — 1.93 meters
Q5 1 Mark

A surveyor measures the angle of elevation to the top of a hill as 45°. If he is standing 100 meters away from the base of the hill, what is the height of the hill?

A50 meters
B100 meters
C70.71 meters
D141.42 meters
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Correct answer: Option 2 — 100 meters
Q6 3 Marks

Define the angle of elevation and provide an example of its application in real life.

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The angle of elevation is the angle formed between the horizontal line and the line of sight to an object above the horizontal level. For example, when standing on the ground and looking up at the top of a building, the angle formed is the angle of elevation.
Q7 3 Marks

A person is standing 30 meters away from a tree. If the angle of elevation from the ground to the top of the tree is 60 degrees, calculate the height of the tree.

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Using the tangent function, height = distance * tan(angle). Here, height = 30 * tan(60°) = 30 * √3 ≈ 51.96 meters.
Q8 3 Marks

Explain the concept of the angle of depression and how it differs from the angle of elevation.

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The angle of depression is the angle formed between the horizontal line and the line of sight to an object below the horizontal level. It differs from the angle of elevation, which measures the angle to an object above the horizontal line.
Q9 3 Marks

A surveyor is standing at point A and observes a tower at point B. If the angle of depression from point A to the top of the tower is 45 degrees and the height of the tower is 20 meters, how far is the surveyor from the base of the tower?

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Using the angle of depression, the distance from the base of the tower can be calculated using the formula: distance = height / tan(angle). Here, distance = 20 / tan(45°) = 20 meters.
Q10 3 Marks

Describe a real-life scenario where trigonometric ratios can be used to solve a height and distance problem.

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A real-life scenario could involve a firefighter using a ladder to reach a window. If the ladder makes a 60-degree angle with the ground and the base of the ladder is 5 meters from the wall, the firefighter can use trigonometric ratios to calculate the height of the window using the sine function: height = 5 * tan(60°).
Q11 6 Marks

A person is standing 50 meters away from the base of a tree. If the angle of elevation from the person's eyes to the top of the tree is 30 degrees, calculate the height of the tree. Show your calculations and explain the steps involved.

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To find the height of the tree, we can use the tangent of the angle of elevation. The formula is: height = distance * tan(angle). Here, the distance is 50 meters and the angle is 30 degrees. Therefore, height = 50 * tan(30 degrees) = 50 * (1/√3) = 50/√3 ≈ 28.87 meters. Thus, the height of the tree is approximately 28.87 meters.
Q12 6 Marks

A tower stands on a hill. From a point on the ground, the angle of elevation to the top of the tower is 45 degrees. If the height of the tower is 20 meters, calculate the distance from the point on the ground to the base of the tower. Provide a detailed explanation of your calculations.

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Using the tangent function, we know that tan(angle) = opposite/adjacent. Here, the opposite side is the height of the tower (20 meters) and the angle is 45 degrees. Since tan(45 degrees) = 1, we have 1 = 20/distance. Therefore, distance = 20 meters. This means the distance from the point on the ground to the base of the tower is 20 meters.
Q13 6 Marks

A surveyor is measuring the height of a building. He stands 100 meters away from the base of the building and measures the angle of elevation to the top of the building to be 60 degrees. Calculate the height of the building and explain the trigonometric principles used in your calculations.

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To find the height of the building, we can use the tangent function. The formula is height = distance * tan(angle). Here, the distance is 100 meters and the angle is 60 degrees. Thus, height = 100 * tan(60 degrees) = 100 * √3 ≈ 173.21 meters. The height of the building is approximately 173.21 meters. This calculation uses the relationship between the angle of elevation and the tangent ratio in a right triangle.
Q14 6 Marks

A kite is flying at a height of 80 meters. The angle of depression from the kite to a point on the ground is 30 degrees. Calculate the horizontal distance of the kite from the point directly below it on the ground. Include a detailed explanation of your method.

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To find the horizontal distance, we can use the angle of depression. The height of the kite is the opposite side (80 meters) and the angle is 30 degrees. Using the tangent function, we have tan(30 degrees) = opposite/adjacent. Therefore, adjacent = opposite/tan(30 degrees) = 80/(1/√3) = 80√3 ≈ 138.56 meters. The horizontal distance of the kite from the point directly below it is approximately 138.56 meters.
Q15 6 Marks

From the top of a cliff, the angle of depression to a boat in the sea is measured to be 45 degrees. If the height of the cliff is 100 meters, calculate the distance of the boat from the base of the cliff. Provide a thorough explanation of your calculations.

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Using the angle of depression, we can find the distance to the boat. The height of the cliff (100 meters) is the opposite side, and the angle is 45 degrees. Since tan(45 degrees) = 1, we have 1 = 100/distance. Thus, distance = 100 meters. Therefore, the distance of the boat from the base of the cliff is 100 meters. This calculation illustrates the relationship between the angle of depression and the tangent function in a right triangle.
Q16 1 Mark

Assertion (A): The angle of elevation is the angle formed by the line of sight and the horizontal line when looking upwards.

Reason (R): The angle of depression is measured from the horizontal line downwards.

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Correct answer: Option 1 — Both A and R are true, and R is the correct explanation of A.
Q17 1 Mark

Assertion (A): To find the height of a tree using trigonometry, one can use the angle of elevation from a certain distance.

Reason (R): The height of the tree can be calculated using the tangent ratio of the angle of elevation.

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Correct answer: Option 1 — Both A and R are true, and R is the correct explanation of A.
Q18 1 Mark

Assertion (A): The line of sight is always horizontal regardless of the observer's position.

Reason (R): The line of sight can be inclined depending on whether the observer is looking up or down.

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Correct answer: Option 4 — A is false, but R is true.
Q19 1 Mark

Assertion (A): In a right triangle, the sine of an angle is equal to the opposite side divided by the hypotenuse.

Reason (R): The cosine of an angle is defined as the adjacent side divided by the hypotenuse.

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Correct answer: Option 2 — Both A and R are true, but R is not the correct explanation of A.
Q20 1 Mark

Assertion (A): The angle of depression from the top of a building to a point on the ground is equal to the angle of elevation from that point to the top of the building.

Reason (R): This is due to the alternate interior angles being equal when a transversal intersects two parallel lines.

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Correct answer: Option 1 — Both A and R are true, and R is the correct explanation of A.
Q21 1 Mark

Statement 1: The angle of elevation is the angle formed by the line of sight and the horizontal line when looking up at an object.

Statement 2: The angle of depression is the angle formed by the line of sight and the horizontal line when looking down at an object.

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Correct answer: Option 1 — Both statements are true.
Q22 1 Mark

Statement 1: To find the height of a tree using trigonometry, one can use the tangent ratio if the distance from the tree is known and the angle of elevation is measured.

Statement 2: The sine ratio is the most appropriate trigonometric ratio to find the height of a tree when the angle of elevation is known.

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Correct answer: Option 3 — Only Statement 2 is true.
Q23 1 Mark

Statement 1: In surveying, the angle of depression is used to measure the height of a building from a distance.

Statement 2: The line of sight is always horizontal when measuring angles of elevation.

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Correct answer: Option 4 — Both statements are false.
Q24 1 Mark

Statement 1: The height of an object can be calculated using the cosine ratio when the angle of elevation and the distance from the object are known.

Statement 2: Trigonometric ratios can only be applied in right-angled triangles.

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Correct answer: Option 2 — Only Statement 1 is true.
Q25 1 Mark

Statement 1: If the angle of elevation increases, the height of the object must also increase if the distance remains constant.

Statement 2: The tangent of an angle in a right triangle is the ratio of the opposite side to the adjacent side.

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Correct answer: Option 1 — Both statements are true.

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