Class 10 Exam  >  Class 10 Notes  >  Mathematics (Maths) Class 10  >  Important Definitions & Formulas: Some Applications of Trigonometry

Important Definitions & Formulas: Some Applications of Trigonometry | Mathematics (Maths) Class 10 PDF Download

Introduction

In Chapter 9, Class 10 students will learn how to use trigonometry to find the height and distance of objects without measuring them directly. In the past, astronomers relied on trigonometry to calculate distances between planets, Earth, and stars. This chapter explores various ways trigonometry is applied in everyday life.

Topics covered in this chapter include:

  • Heights and distances
  • The line of sight
  • The angle of elevation
  • The horizontal line
  • The angle of depression

By using trigonometric ratios, we can determine the height or length of an object or the distance between two far-away objects.

Horizontal Level  

The horizontal level refers to the straight line that runs through the observer's eye.Important Definitions & Formulas: Some Applications of Trigonometry | Mathematics (Maths) Class 10

This doc is part of
127 videos|550 docs|75 tests
Join course for free

Line of Sight

The line which is drawn from the eyes of the observer to the point being viewed on the object is known as the line of sight.

Angle of Elevation

The Angle of elevation of the point viewed is the angle formed by the line of sight with the horizontal when the point being viewed is above the horizontal level, i.e., the case when we raise our head to look at the object.

Angle of Depression

The angle of depression of a point on the object being viewed is the angle formed by the line of sight with the horizontal when the point is below the horizontal level, i.e., the case when we lower our head to look at the point being viewed.
Important Definitions & Formulas: Some Applications of Trigonometry | Mathematics (Maths) Class 10

Height and Distance Formulas for Trigonometric ratio

ΔABC is a right-angled triangle where the side AB is the vertical side, AC is the longest side (the hypotenuse), and BC is the horizontal side.

The trigonometric ratios are defined as follows:

  • Sin θ = AB/AC
  • Cos θ = BC/AC
  • Tan θ = AB/BC
  • Cosec θ = AC/AB
  • Sec θ = AC/BC
  • Cot θ = BC/AB

Trigonometrical Identities:

  • sin2θ + cos2 θ = 1
  • 1 + tan2θ = sec2 θ
  • 1 + cot2θ = cosec2 θ
Important Definitions & Formulas: Some Applications of Trigonometry | Mathematics (Maths) Class 10
Download the notes
Important Definitions & Formulas: Some Applications of Trigonometry
Download as PDF
Download as PDF


Some Examples Using Above Formulas


Q1: Adam is standing in the Sun. He is 6ft tall and is casting a shadow of 4ft. A flag is also present near the man casting a shadow of 36ft. Calculate the height of the flag.
Ans: The angle of elevation for the Sun will be the same for both the cases.
Therefore, the ratio of object to shadow will be the same for both the cases as per the proportionality rule.
Object height/ Shadow height = 6/ 4 = H /36
Therefore, H = 54 ft = Height of the flag
Important Definitions & Formulas: Some Applications of Trigonometry | Mathematics (Maths) Class 10

Q2: When a boy looks from the foot and the top of a tower at the roof of a building, the angles of elevation and depression are 227o and 63o, The height of this building is 40m, then calculate the height of the tower given that tan 630 =2.
Ans: Let the tower be AB
Let the building of height 40m be CD
In the given triangle ACD, AC/DC = cot 270
= cot (90-63)
AC/40 = tan 630 = 2
AC = 80m
Now, DE = AC = 80m
Also, in triangle BED, tan 630 = BE/DE
2= BE/80
Therefore, BE = 160 m
Therefore, the height of the tower can be calculated as AE + EB
= 40 +160 = 200m
Important Definitions & Formulas: Some Applications of Trigonometry | Mathematics (Maths) Class 10

The document Important Definitions & Formulas: Some Applications of Trigonometry | Mathematics (Maths) Class 10 is a part of the Class 10 Course Mathematics (Maths) Class 10.
All you need of Class 10 at this link: Class 10
Are you preparing for Class 10 Exam? Then you should check out the best video lectures, notes, free mock test series, crash course and much more provided by EduRev. You also get your detailed analysis and report cards along with 24x7 doubt solving for you to excel in Class 10 exam. So join EduRev now and revolutionise the way you learn!
Sign up for Free Download App for Free
127 videos|550 docs|75 tests

Up next

FAQs on Important Definitions & Formulas: Some Applications of Trigonometry - Mathematics (Maths) Class 10

1. What are the key trigonometric ratios used in height and distance problems?
Ans. The key trigonometric ratios used in height and distance problems are sine (sin), cosine (cos), and tangent (tan). These ratios are defined as follows: - \( \sin \theta = \frac{\text{Opposite Side}}{\text{Hypotenuse}} \) - \( \cos \theta = \frac{\text{Adjacent Side}}{\text{Hypotenuse}} \) - \( \tan \theta = \frac{\text{Opposite Side}}{\text{Adjacent Side}} \) These ratios help in finding heights and distances in right-angled triangles.
2. How can we calculate the height of a tree using trigonometry?
Ans. To calculate the height of a tree using trigonometry, measure the distance from the tree (let's call it \( d \)) and the angle of elevation (\( \theta \)) from the ground to the top of the tree. The height (\( h \)) can be calculated using the formula: \[ h = d \cdot \tan \theta \] This formula arises from the tangent ratio, where the height of the tree is the opposite side, and the distance from the tree is the adjacent side.
3. What is the formula to find the distance of an object from a point when the angle of depression is known?
Ans. When the angle of depression (\( \theta \)) from a point to an object is known, the distance (\( d \)) to the object can be calculated using the formula: \[ d = h \cdot \tan \theta \] where \( h \) is the height from which the angle is measured. This is derived from the tangent ratio in the right-angled triangle formed by the height and the distance to the object.
4. What role does the angle of elevation play in solving height and distance problems?
Ans. The angle of elevation is the angle formed between the horizontal line and the line of sight to an object above the horizontal line. In height and distance problems, it is crucial for determining the height of an object when the distance from the object is known. The relationship can be expressed using the tangent function: \[ \tan \theta = \frac{\text{Height}}{\text{Distance}} \] This helps in finding unknown heights by rearranging the formula based on known values.
5. Can you explain the relationship between angles of elevation and depression?
Ans. The angle of elevation and the angle of depression are related in that they are equal when measured from a horizontal line. The angle of elevation is measured upwards from the horizontal to a point above, while the angle of depression is measured downwards from the horizontal to a point below. In practical problems, if you know the angle of elevation from point A to point B, the angle of depression from point B to point A will be the same, which can be useful in solving height and distance problems.
127 videos|550 docs|75 tests
Download as PDF

Up next

Explore Courses for Class 10 exam
Related Searches

Important Definitions & Formulas: Some Applications of Trigonometry | Mathematics (Maths) Class 10

,

pdf

,

Viva Questions

,

practice quizzes

,

shortcuts and tricks

,

Important Definitions & Formulas: Some Applications of Trigonometry | Mathematics (Maths) Class 10

,

Extra Questions

,

Objective type Questions

,

Semester Notes

,

mock tests for examination

,

Important Definitions & Formulas: Some Applications of Trigonometry | Mathematics (Maths) Class 10

,

past year papers

,

Important questions

,

Free

,

Previous Year Questions with Solutions

,

video lectures

,

Sample Paper

,

ppt

,

Summary

,

MCQs

,

Exam

,

study material

;