NCERT Solutions for Class 10 Maths Chapter 8 Introduction to Trigonometry Ex 8.4 are part of NCERT Solutions for Class 10 Maths. Here we have given NCERT Solutions for Class 10 Maths Chapter 8 Introduction to Trigonometry Ex 8.4.

Board |
CBSE |

Textbook |
NCERT |

Class |
Class 10 |

Subject |
Maths |

Chapter |
Chapter 8 |

Chapter Name |
Introduction to Trigonometry |

Exercise |
Ex 8.4 |

Number of Questions Solved |
5 |

Category |
NCERT Solutions |

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

**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) \(\frac{1+\tan ^{2} A}{1+\cot ^{2} A}\)

(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:

Solution:

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