# NCERT Solutions For Class 10 Maths Chapter 8 Introduction to Trigonometry Ex 8.4

Here, Below you all know about NCERT Solutions for Class 10 Maths Chapter 8 Introduction to Trigonometry Ex 8.4 Question Answer. I know many of you confuse about finding Chapter 8 Introduction to Trigonometry Ex 8.4 Of Class 10 NCERT Solutions. So, Read the full post below and get your solutions.

## NCERT Solutions for Class 10 Maths Chapter 8 Introduction to Trigonometry Ex 8.4

NCERT TEXTBOOK EXERCISES

Question 1. Express the trigonometric ratios sin A, sec A and tan A in terms of cot A.

Solution:

From trigonometric identity, cosec² A – cot² A = 1, we get

Question 2. Write all the other trigonometric ratios of ∠A in terms of sec A.

Solution:

Since sin² A + cos² A = 1, therefore

Question 3. Evaluate:

(I)

(ii) sin 25° cos 65° + cos 25° sin 65°

Solution:

(ii) sin 25° cos 65° + cos 25° sin 65° = sin 25° cos (90° – 25°) + cos 25° sin (90° – 25°)
= sin 25° sin 25° + cos 25° cos 25°
= sin² 25° + cos² 25° = 1

Question 4. Choose the correct option. Justify your choice.

(i) 9 sec² A – 9 tan² A =
(A) 1
(B) 9
(C) 8
(D) 0

(ii) (1 + tan θ + sec θ) (1 + cot θ – cosec θ ) =
(A) 0
(B) 1
(C) 2
(D) -1

(iii) (sec A + tan A) (1 – sin A) =
(A) sec A
(B) sin A
(C) cosec A
(D) cos A

(iv) 1+tan2A1+cot2A
(A) sec² A
(B) -1
(C) cot² A
(D) tan² A

Solution:

(i) 9 sec² A – 9 tan² A = 9(sec² A – tan² A) = 9 x 1 = 9
Correct option is (B)

Question 5. Prove the following identities, where the angles involved are acute angles for which the expressions are defined.

Solution:

## NCERT Solutions for Class 10 Maths Chapter 8 Introduction to Trigonometry Exercise 8.4 PDF

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