Page 33 - Mathematics Class - XI

Viva-Voce

1. Name the quadrant in which all trigonometric functions are positive.
Ans. First quadrant.
2. What are the values of sin (–q) and cos (–q)?

Ans. sin (–q) = –sin q and cos (–q) = cos q
3. Name the trigonometric functions which are negative in fourth quadrant.
Ans. tan, cot, sine and cosecant
 5π  5π
4. Find the exact values of sin   and cos   .
 3   3 

Ans. sin 5 sin 2 sin 3 and cos 5 cos 2 cos 1

3 3 3 2 3 3 3 2
5. What is meant by trigonometric identity?
Ans. Trigonometric identities are equalities that involve trigonometric functions and are true for every value of
the occurring variables where both sides of the equality are defined.
6. What are the trigonometric identities in square forms?
Ans. (i) cos x + sin x = 1
2
2
(ii) 1 + tan x = sec x
2
2
(iii) 1 + cot x = cosec x
2
2
7. What is the value of sin (2 np + x)?
Ans.  sin (2 np + x) = sin x

MCQs

1. If sinq + cosecq = 2, then sin q + cosec q equals to
2
2
a) 1 b) 4 c) 2 d) None of these
2. sin (90° + q) = ?

a) cosq b) –cosq c) sinq d) –sinq
3. tan (180° + q) = ?
a) tanq b) –tanq c) cotq d) –cotq
4. Which of the following is not true

1
a) sinq = − b) cosq = 1 c) secq = 1 d) tanq = 20
5 2
5. tan 1°, tan 2°, tan 3° .............. tan 89° is equal to
a) 0 b) 1 c) 3 d) Not defined

1
Answers: 1. c) 2 2. a) cosq 3. a) tanq 4. c) secq = 5. b) 1
2
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