# NCERT Solutions for Class 10 Maths Chapter 8 - Introduction to Trigonometry

Relearn the concepts in the Maths syllabus with our NCERT Solutions for CBSE Class 10 Mathematics Chapter 8 Introduction to Trigonometry. Your trigonometry skills will be extremely useful if you aspire to have a rewarding career in the engineering stream. Practise the solutions written by our Maths experts to understand the application of the Pythagoras’ theorem to solve trigonometry problems.

To strengthen your trigonometry basics, explore TopperLearning’s CBSE Class 10 Maths concept videos and chapter notes. Our sample papers and Maths past years’ question papers are also useful for exam preparation.

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## Chapter 8 - Introduction to Trigonometry Exercise Ex. 8.1

Solution 1

In ABC by applying Pythagoras theorem
AC2 = AB2 + BC2
= (24)2 + (7)2
= 576 + 49
= 625
AC = = 25 cm    Solution 2 Solution 3 Solution 4 Solution 5 Solution 6

Since A and B are acute angles, then C is a right angle.

cos A = cos B .... given

AC/AB = BC/AB

AC = BC B = A           .... angles opposite to equal sides are equal in length.

Solution 7 Solution 8 Solution 9 Solution 10 Solution 11   ## Chapter 8 - Introduction to Trigonometry Exercise Ex. 8.2

Solution 1 Solution 2  Solution 3 Solution 4 ## Chapter 8 - Introduction to Trigonometry Exercise Ex. 8.3

Solution 1 Solution 2 Solution 3

Given that

tan 2A = cot (A - 18)

cot (90 - 2A) = cot (A -18)
90 - 2A = A - 18
108 = 3A
A = 36

Solution 4

Given that
tan A = cot B
tan A = tan (90 - B)
A = 90 - B
A + B = 90

Solution 5

Given that
Sec 4A = cosec (A - 20)
Cosec (90 - 4A) = cosec (A - 20)
90 - 4A = A - 20
110 = 5A
A = 22

Solution 6 Solution 7

sin 67 + cos 75
= sin (90 - 23) + cos (90 - 15)
= cos 23 + sin 15

## Chapter 8 - Introduction to Trigonometry Exercise Ex. 8.4

Solution 1
We know that Solution 2
We know that Solution 3 Solution 4

(i) 9sec2A - 9tan2A
= 9(sec2A - tan2A)
= 9 (1)            (as sec2A - tan2A = 1)
= 9
Hence alternative (B) is correct.

(ii) (1 + tanθ + secθ) (1 + cotθ - cosecθ) Hence alternative (C) is correct.

(iii) (secA + tanA) (1 - sinA) (iv) Solution 5           ### STUDY RESOURCES

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