# 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, cosecÂ² A â€“ cotÂ² A = 1, we get

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

Solution:

Since sinÂ² A + cosÂ² A = 1, therefore

Question 3. Evaluate:

(I)

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

Solution:

(ii) sin 25Â° cos 65Â° + cos 25Â° sin 65Â° = sin 25Â° cos (90Â° â€“ 25Â°) + cos 25Â° sin (90Â° â€“ 25Â°)
= sin 25Â° sin 25Â° + cos 25Â° cos 25Â°
= sinÂ² 25Â° + cosÂ² 25Â° = 1

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

(i) 9 secÂ² A â€“ 9 tanÂ² A =
(A) 1
(B) 9
(C) 8
(D) 0

(ii) (1 + tan Î¸ + sec Î¸) (1 + cot Î¸ â€“ cosec Î¸ ) =
(A) 0
(B) 1
(C) 2
(D) -1

(iii) (sec A + tan A) (1 â€“ sin A) =
(A) sec A
(B) sin A
(C) cosec A
(D) cos A

(iv)Â 1+tan2A1+cot2A
(A) secÂ² A
(B) -1
(C) cotÂ² A
(D) tanÂ² A

Solution:

(i) 9 secÂ² A â€“ 9 tanÂ² A = 9(secÂ² A â€“ tanÂ² 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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