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NCERT Solutions for class 11 Maths | Chapter 3 - Trigonometric Functions

(1) Find all angles θ such that -2π < θ < 2π and cos θ = √2 / 2
[A] {-7 π / 4, - π / 4 , π / 4 , 7 π / 4}
[B] {- π / 4, - 3 π / 4 , π / 4 , 3 π / 4}
[C] {-5 π / 4, π / 4 , 3 π / 4}
[D] {π / 4 , π / 4 , 3 π / 4}
Answer: {-7 π / 4, - π / 4 , π / 4 , 7 π / 4}
(2) If sin t = 1/5 and 0 < t < π/ 2, then cos (4 t) = ?
[A] 0.3464
[B] 0.8
[C] 0.6928
[D] - 0.6928
Answer: 0.6928

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(3) If cos t = 1/3 and 3π /2 < t < 2π in quadrant IV, then sin (4 t) = ?
[A] 8 √2 / 3
[B] - 8 √2 / 3
[C] - 56 √2 / 243
[D] 56 √2 / 81
Answer: 56 √2 / 81
(4) If cos t = 3/4, and sin t < 0, then sin (3 t) = ?
[A] √7 / 16
[B] - 5 √7 / 16
[C] - 3 √7 / 4
[D] 5 √7 / 16
Answer: - 5 √7 / 16
(5) If tan x = 5, then tan (2 x) = ?
[A] 10
[B] - 5 / 12
[C] 1 / 10
[D] 5 / 12
Answer: - 5 / 12
(6) If cos t = 0.8, then cos (2 t) = ?
[A] 0.28
[B] 0.4
[C] 1.0
[D] 1.6
Answer: 0.28
(7) If sin t = 0.6 and cot t > 0, then sin (2 t) = ?
[A] - 0.96
[B] 0.48
[C] 0.96
[D] - 0.48
Answer: 0.96
(8) Which of the following is not correct?
[A] sin(x) = -sin(-x)
[B] sec(-t) = sec(t)
[C] sin(π + x) = sin(x)
[D] cos(π - x) = -cos(x)
Answer: sin(π + x) = sin(x)
(9) Which of the following is not the same as tan(t)?
[A] - tan(-t)
[B] tan(t + 2π)
[C] tan(t + π)
[D] tan(t + π / 2)
Answer: tan(t + π / 2)
(10) If sin(-t) = 0.54, what is - sin(t) ?
[A] 0.54
[B] -0.54
[C] - 0.46
[D] 0.46
Answer: 0.54
(11) If cos(-t) = 0.34, what is cos(t) ?
[A] -0.34
[B] 0.66
[C] 0.34
[D] - 0.66
Answer: 0.34
(12) If 0 < t < π/2 and sin t = 0.65, what is sin(t + π) ?
[A] -0.65
[B] 0.65
[C] 0.35
[D] 0.76
Answer: -0.65
(13) cos(x) + cos(π - x) =?
[A] 2 cos(x)
[B] cos(x) - sin(x)
[C] cos(x) + sin(x)
[D] 0
Answer: 0
(14) If tan(t) = 13, then cot(-t) =?
[A] 13
[B] 1 / 13
[C] - 1 / 13
[D] - 13
Answer: - 1 / 13
(15) If 0 < t < π / 2 and sin t = 0.35, then cos(t + π) =?
[A] 0.94
[B] -0.94
[C] 0.81
[D] -0.81
Answer: -0.94
(16) If point (a , b) is on the Unit Circle associated with the rotation t, then the point on the Unit circle associated with rotation t + π / 2, has the following coordinates
[A] (b , a)
[B] (-b , a)
[C] (-b , -a)
[D] (-a , b)
Answer: (-b , a)
(17) If point (a , b) is on the Unit Circle associated with the rotation t and point (c , d) is also on the Unit circle associated with rotation t + π, then which of the following is correct?
[A] c = - a and d = - b
[B] c = - a and d = b
[C] c = a and d = b
[D] c = a and d = - b
Answer: c = - a and d = - b
(18) If point (a , b) is on the Unit Circle associated with the rotation t, which of the following is not correct?
[A] sin(t) = b
[B] cos(t) = a
[C] sin(-t) = - a
[D] cos(-t) = - a
Answer: cos(-t) = - a
(19) Find the point on the Unit Circle associated with the angle 5π/3
[A] (1 / 2 , 1 / 2)
[B] (-√3 / 2 , 1/2)
[C] (1 / 2 , -√3 / 2)
[D] (-√3 / 2 , -1/2)
Answer: (1 / 2 , -√3 / 2)
(20) Find the point on the Unit Circle associated with the rotation -9π/2
[A] (0 , -1)
[B] (0 , 1)
[C] (1 , 0)
[D] (-1 , 0)
Answer: (-1 , 0)

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