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NCERT - Mathematics

Book: NCERT - Mathematics

Chapter: 8. Introduction to Trigonometry

Subject: Maths - Class 10^th

Q. No. 4 of Exercise 8.4

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4

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Following is the explanation:

9 sec² A – 9 tan² A

= 9 (sec² A – tan² A)

= 9 x 1

= 9

5

Chapter Exercises

Exercise 8.1

Exercise 8.2

Exercise 8.3

Exercise 8.4

Testing

1

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

2

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

3

Evaluate:

(i)

(ii) Sin 25° Cos 65° + Cos 25° Sin 65°

4

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4

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4

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(Sec A + tan A) (1 – sin A) =

4

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5

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

(i)

(ii)

(iii)

(iv)

(v) using the identity

(vi)

(vii)

(viii)

(ix) [Hint: Simplify LHS and RHS separately]

(x)