# Introduction to Trigonometry – Class X – Part 5 | Exercise 8.2 Q2-4 Solved

### Watch the fifth video session on “Introduction To Trigonometry” for Class Xth – concepts and solved questions

Introduction To Trigonometry – Class X – Part 5

1. How to remember trigonometric ratios for specific angles: 0°,30°,45°, 60°, 90°:

a) Just remeber the values for Sin of the angles.
b) The values for cos will be in reverse order of Sin of the angles.
c) Tan of angle = Sine of angle/ Cos of angle
d) Cosec is reciprocal of Sin.
e) Sec is reciprocal of cos.
f) Cot is reciprocal of tan.

NCERT Exercise 8.2 Q2-4 Solved

2. Choose the correct option and justify your choice :

(i) 2 tan 30°/ (1 + tan230°) =

(A) sin 60° (B) cos 60° (C) tan 60° (D) sin 30°

(ii) (1 – tan245°)/ (1 + tan245°) =

(A) tan 90° (B) 1 (C) sin 45° (D) 0

(iii) sin 2A = 2 sin A is true when A =

(A) 0° (B) 30° (C) 45° (D) 60°

(iv) 2 tan 30°/ (1 – tan230°) =

(A) cos 60° (B) sin 60° (C) tan 60° (D) sin 30°

3. If tan (A + B) = √3 and tan (A – B) = 1/√3 ; 0° ＜ A + B ＜=90°; A ＞ B, find A and B.

4. State whether the following are true or false. Justify your answer.

(i) sin (A + B) = sin A + sin B.

(ii) The value of sin θ increases as θ increases.

(iii) The value of cos θ increases as θ increases.

(iv) sin θ = cos θ for all values of θ.

(v) cot A is not defined for A = 0°.

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