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

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

## PSEB 10th Class Maths Solutions Chapter 8 Introduction to Trigonometry Ex 8.4

Question 1.

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

Solution:

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

= sin 25° × cos (90° – 25°)

+ cos 25° × sin (90° – 25°)

[∵ cos (90° – θ) = sin θ

sin(90° – θ) = cos θ].

= sin 25° × sin 25° + cos 25° × cos 25°

= sin^{2} 25° + cos^{2} 25° = 1.

Question 4.

Choose the correct option. Justify your choice:

(i) 9 sec^{2} A – 9 tan^{2} A =

(A) 1

(B) 9

(C) 8

(D) 0.

(ii) (1 + tan θ + sec θ) (1 + cot θ – cosec θ) =

(A) θ

(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.

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