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JEE • MATHEMATICS • TRIGONOMETRIC EQUATIONS

Trigonometric equations practice · Mixed difficulty

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121 Medium
121 of 581
Analyzing +4 | -1
The set of all values of λ\lambda for which the equation cos⁡22x−2sin⁡4x−2cos⁡2x=λ\cos ^2 2 x-2 \sin ^4 x-2 \cos ^2 x=\lambda has a real solution xx, is
View answer and explanation
Correct option: B
[−32,−1]\left[-\frac{3}{2},-1\right]
Option B ([−32,−1]\left[-\frac{3}{2},-1\right]) is correct because it represents the range of the given trigonometric expression after simplification and using the range of cos⁡22x\cos^2 2x.
122 Medium
122 of 581
Application +4 | -1
The values of aa for which the equation cos⁡4x−(a+2)cos⁡2x−(a+3)=0\cos ^4 x-(a+2) \cos ^2 x-(a+3)=0 possesses a solution, lies in
View answer and explanation
Correct option: A
[−3,−2][-3,-2]
Option A ([-3,-2]) is correct because by solving the quadratic equation for cos⁡2x\cos^2 x and using the fact that 0≤cos⁡2x≤10 \leq \cos^2 x \leq 1, we find that −3≤a≤−2-3 \leq a \leq -2 for the equation to possess a solution.
123 Easy
123 of 581
Application +4 | -1
If 2  cos⁡2  x+3  sin⁡  x−3=0,   0≤  x  ≤180∘2\,\,{\cos ^2}\,\,x + 3\,\,\sin \,\,x - 3 = 0,\;\,0 \le \,\,x\,\, \le 180^\circ, then the value of xx is

View answer and explanation
Correct option: A
30∘,  90∘,   150∘30^\circ ,\,\,90^\circ ,\;\,150^\circ
Option A (30∘,,90∘,;,150∘30^\circ ,\\,90^\circ ,\\;\\,150^\circ) is correct because these are the solutions to the trigonometric equation within the given range.
124 Easy
124 of 581
Application +4 | -1
If sin⁡  2x  cos⁡  2x  cos⁡  4x=λ\sin \,\,2x\,\,\cos \,\,2x\,\,\cos \,\,4x = \lambda has a solution, then λ\lambda lies in the interval
View answer and explanation
Correct option: B
[−1/4,  1/4]\left[ { - 1/4,\;1/4} \right]
Option B ([ - 1/4, 1/4 ]) is correct because the range of sin⁡8x\sin 8x is [-1, 1], which constrains the possible values of λ\lambda.
125 Easy
125 of 581
Understanding +4 | -1
The most general value of θ\theta satisfying the equations sin⁡  θ=sin⁡  α\sin \,\,\theta = \sin \,\,\alpha and cos⁡  θ=cos⁡  α\cos \,\,\theta = \cos \,\,\alpha is
View answer and explanation
Correct option: C
nπ+αn\pi + \alpha
Option A (2nπ+α2n\pi + \alpha) is correct because it represents the general solution where θ\theta and α\alpha have the same sine and cosine values, indicating they are coterminal angles.
126 Easy
126 of 581
Application +4 | -1
cos⁡23π5+cos⁡24π5\cos ^2 \frac{3 \pi}{5}+\cos ^2 \frac{4 \pi}{5} is equal to
View answer and explanation
Correct option: D
34\frac{3}{4}
Option D (34\frac{3}{4}) is correct because using the trigonometric identities and values, the expression simplifies to 34\frac{3}{4}.
127 Medium
127 of 581
Application +4 | -1
 △ABC\triangle A B C is such that sin⁡(2A+B)=12\sin (2 A+B)=\frac{1}{2}.
If A,BA, B and CC are in AP, then the values of A,BA, B and CC are
View answer and explanation
Correct option: A
π4,π3,5π12\frac{\pi}{4}, \frac{\pi}{3}, \frac{5 \pi}{12}
Option A (π4,π3,5π12\frac{\pi}{4}, \frac{\pi}{3}, \frac{5 \pi}{12}) is correct because by using the given condition and the properties of an arithmetic progression, we can find the values of A, B, and C.
128 Medium
128 of 581
Application +4 | -1
If cot⁡xcoty⁡=k\cot x \operatorname{coty}=k and x+y=π/3x+y=\pi / 3, then tan⁡x,tan⁡y\tan x, \tan y satisfy the equation
View answer and explanation
Correct option: A
kt2−3(k−1)t+1=0k t^{2}-\sqrt{3}(k-1) t+1=0
Option A is correct because it represents the quadratic equation whose roots are tan⁡x\tan x and tan⁡y\tan y, derived from the given conditions cot⁡xcot⁡y=k\cot x \cot y = k and x+y=π/3x + y = \pi/3.
129 Medium
129 of 581
Analyzing +4 | -1
If sin⁡6x=1+cos⁡43x\sin ^6 x=1+\cos ^4 3 x, then xx is equal to
View answer and explanation
Correct option: C
(2n+1)π2,n∈I(2 n+1) \frac{\pi}{2}, n \in I
Option C ((2n+1)π2,n∈I(2 n+1) \frac{\pi}{2}, n \in I) is the correct solution because it satisfies both sin⁡6x=1\sin^6 x = 1 and cos⁡43x=0\cos^4 3x = 0.
130 Medium
130 of 581
Analyzing +4 | -1
The most general values of θ\theta satisfying the equation (1+2sin⁡θ)2+(3tan⁡θ−1)2=0(1+2 \sin \theta)^2+(\sqrt{3} \tan \theta-1)^2=0 is/are given by
View answer and explanation
Correct option: C
2nπ+7π62 n \pi+\frac{7 \pi}{6}
Option C (6) is correct because solving the equation tan⁡x+cot⁡x=2csc⁡x\tan x + \cot x = 2 \csc x leads to cos⁡x=12\cos x = \frac{1}{2}, which has 6 solutions in the interval [−2π,2π][-2\pi, 2\pi].
131 Medium
131 of 581
Application +4 | -1
If the equations sin⁡θ=−12\sin \theta=-\frac{1}{2} and tan⁡θ=13\tan \theta=\frac{1}{\sqrt{3}}, then most common general value of θ\theta is
View answer and explanation
Correct option: C
2nπ+7π62 n \pi+\frac{7 \pi}{6}
Option C (2nπ+7π62 n \pi+\frac{{7 \pi}}{{6}}) is correct because it represents the general solution that satisfies both the sine and tangent equations.
132 Easy
132 of 581
Application +4 | -1
The number of roots of the equation, (81)sin⁡2x+(81)cos⁡2x=30{\left( {81} \right)^{\sin }}^{^2x} + {\left( {81} \right)^{\cos }}^{^2x} = 30 in the interval [0, π]\left[ {0,\,\pi } \right] is equal to:
View answer and explanation
Correct option: C
4
Option C (4) is correct because solving the trigonometric equation yields four solutions within the specified interval [0, π].
133 Easy
133 of 581
Application +4 | -1
The value of the expression (3sin⁡75∘−cos⁡75∘)\left(\sqrt{3} \sin 75^{\circ}-\cos 75^{\circ}\right) is
View answer and explanation
Correct option: D
2\sqrt{2}
The correct answer is 2\sqrt{2} because the expression simplifies to 2sin⁡45∘2 \sin 45^{\circ}, which equals 2\sqrt{2}.
134 Medium
134 of 581
Application +4 | -1
The most general values of xx for which 3sin⁡x−cos⁡x=min⁡λεR{2,e2,π,λ2−4λ+7}\sqrt{3} \sin x-\cos x=\min \limits_{\lambda \varepsilon {R}}\left\{2, {e}^2, \pi, \lambda^2-4 \lambda+7\right\} are given by-
View answer and explanation
Correct option: B
2nπ+2π32 {n} \pi+\frac{2 \pi}{3}
Option B (2nπ+2π32 {n} \pi+\frac{{2 \pi}}{{3}}) is correct because it represents the general solution to the trigonometric equation after simplification and solving for x.
135 Medium
135 of 581
Application +4 | -1
If tan⁡x=ba\tan x=\frac{b}{a}, then the value of acos⁡2x+bsin⁡2xa \cos 2 x+b \sin 2 x is
View answer and explanation
Correct option: A
aa
Option A (aa) is correct because by substituting tan⁡x=ba\tan x = \frac{{b}}{{a}} into the expression acos⁡2x+bsin⁡2xa \cos 2x + b \sin 2x and using trigonometric identities, the expression simplifies to aa.
136 Medium
136 of 581
Application +4 | -1
The general solution for α\alpha is, if 2sin⁡2α+3cos⁡α+1=02 \sin ^2 \alpha+\sqrt{3} \cos \alpha+1=0
View answer and explanation
Correct option: B
2nπ±5π62 n \pi \pm \frac{5 \pi}{6}
Option B (2nπ±5π62 n \pi \pm \frac{{5 \pi}}{{6}}) is correct because it represents the general solution derived from solving the given trigonometric equation.
137 Medium
137 of 581
Understanding +4 | -1
Which one of the following is not correct?
View answer and explanation
Correct option: C
∣sec⁡x∣<1|\sec x| < 1
The correct answer is ∣sec⁡x∣<1|\sec x| < 1 because the range of sec⁡x\sec x is (−∞,−1]∪[1,∞)(-\infty, -1] \cup [1, \infty), so its absolute value cannot be less than 1.
138 Medium
138 of 581
Analyzing +4 | -1
The graph of the function cos⁡xcos⁡(x+2)−cos⁡2(x+1)\cos x \cos (x+2)-\cos ^2(x+1) is
View answer and explanation
Correct option: D
A straight line passing through the point (π2,−sin⁡21)\left(\frac{\pi}{2},-\sin ^2 1\right) and parallel to the XX-axis
Option D (A straight line passing through the point (π2,−sin⁡21)\left(\frac{\pi}{2},-\sin ^2 1\right) and parallel to the XX-axis) is correct because the given expression simplifies to a constant value, −sin⁡21-\sin^2 1, which represents a horizontal line.
139 Easy
139 of 581
Application +4 | -1
Maximum value of the expression 2sin⁡x+4cos⁡x+32 \sin x+4 \cos x+3 is
View answer and explanation
Correct option: A
25+32 \sqrt{5}+3
Option A (25+32 \sqrt{5}+3) is correct because the maximum value of asin⁡x+bcos⁡xa \sin x + b \cos x is a2+b2\sqrt{a^2 + b^2}, and adding a constant shifts the maximum value accordingly.
140 Medium
140 of 581
Application +4 | -1
1+sin⁡  x+sin⁡2x+…1 + \sin \,\,x + {\sin ^2}x + \ldots to ∞=4+2 3\infty = 4 + 2\,\sqrt 3, if
View answer and explanation
Correct option: A
x=2π3    or,  π3x = \frac{{2\pi }}{3}\,\,\;\mathrm{or,}\,\,\frac{\pi }{3}
Option A (x=2π3    or  π3x = \frac{{2\pi }}{{3}}\,\,\;\mathrm{or}\,\,\frac{\pi }{3}) is correct because it satisfies the given infinite geometric series equation after solving for sin(x).
141 Easy
141 of 581
Application +4 | -1
Sum of the root of the equation 2sin⁡2θ+sin⁡22θ=2;0≤θ≤π/22 \sin ^2 \theta+\sin ^2 2 \theta=2 ; 0 \leq \theta \leq \pi / 2 is
View answer and explanation
Correct option: B
3π/43 \pi / 4
Option B (3π/43 \pi / 4) is correct because by simplifying the given equation and solving for θ\theta in the interval [0,π/2][0, \pi / 2], we find the roots are π/4\pi/4 and π/2\pi/2, and their sum is 3π/43\pi/4.
142 Medium
142 of 581
Analyzing +4 | -1
Let S={θ∈[−π,π]−{±π2}:sin⁡θtan⁡θ+tan⁡θ=sin⁡2θ}.S = \left\{ {\theta \in \left[ { - \pi ,\pi } \right] - \left\{ { \pm \frac{\pi }{2}} \right\}:\sin \theta \tan \theta + \tan \theta = \sin 2\theta } \right\}. If T=∑θ∈Scos⁡2θ,T = \sum\limits_{\theta \in S} {\cos 2\theta } , then T+n(S)T + n\left( S \right) is equal to:
View answer and explanation
Correct option: B
9
The correct answer is 9 because the sum of the cosines of the solutions plus the number of solutions to the trigonometric equation equals 9.
143 Medium
143 of 581
Application +4 | -1
What is sin⁡2(3π)+cos⁡2(4π)+tan⁡2(5π)\sin ^{2}(3 \pi)+\cos ^{2}(4 \pi)+\tan ^{2}(5 \pi) equal to ?
View answer and explanation
Correct option: B
1
Option B (1) is correct because it simplifies to sin⁡2(3π)+cos⁡2(4π)+tan⁡2(5π)=0+1+0=1\sin^2(3\pi) + \cos^2(4\pi) + \tan^2(5\pi) = 0 + 1 + 0 = 1.
144 Medium
144 of 581
Application +4 | -1
The solution of the trigonometric equation cos⁡2(π3cos⁡x−8π3)=1\cos ^2\left(\frac{\pi}{3} \cos x-\frac{8 \pi}{3}\right)=1 must be-
View answer and explanation
Correct option: C
2nπ2 {n} \pi
Option C (2nπ2 {n} \pi) is correct because it represents the general solution to the trigonometric equation after simplification and considering the range of cosine function.
145 Hard
145 of 581
Application +4 | -1
If ∣k∣=5|k|=5 and 0∘≤θ≤360∘0^{\circ} \leq \theta \leq 360^{\circ}, then the number of different solution of 3cos⁡θ+4sin⁡θ=k3 \cos \theta+4 \sin \theta=k is
View answer and explanation
Correct option: B
Two
Option B (Two) is correct because the equation has two solutions when ∣k∣=5|k| = 5 and 0∘≤θ≤360∘0^{\circ} \leq \theta \leq 360^{\circ}.
146 Easy
146 of 581
Application +4 | -1
Number of values of x∈[0,2π]x \in[0,2 \pi] and satisfying the equation
cos⁡xcos⁡2xcos⁡3x=1/4\cos x \cos 2 x \cos 3 x=1 / 4 is:
View answer and explanation
Correct option: B
8
The correct answer is B (8) because solving the trigonometric equation cos⁡xcos⁡2xcos⁡3x=1/4\cos x \cos 2x \cos 3x = 1/4 within the interval [0,2π][0, 2\pi] yields 8 distinct solutions.
147 Easy
147 of 581
Application +4 | -1
If 5x+1>−245 x+1>-24 and 5x−1<245 x-1 < 24, then x∈(−a,a)x \in(-a, a). The value of &#39;aa&#39; is
View answer and explanation
Correct option: A
5
Option A (5) is correct because solving the compound inequality 5x+1>−245x + 1 > -24 and 5x−1<245x - 1 < 24 results in −5<x<5-5 < x < 5, which corresponds to the interval (−5,5)(-5, 5).
148 Medium
148 of 581
Analyzing +4 | -1
If f(x)=cos⁡x(sin⁡x+sin⁡2x+sin⁡2θ),f\left( x \right) = \cos x\left( {\sin x + \sqrt {{{\sin }^2}x + {{\sin }^2}\theta } } \right), where θ\theta is a given constant, then maximum value of f(x)f(x) is
View answer and explanation
Correct option: B
1+sin⁡2θ\sqrt{1+\sin ^2 \theta}
Option B (1+sin⁡2θ\sqrt{1+\sin ^2 \theta}) is correct because by completing the square and using trigonometric identities, we can find the maximum value of f(x)f(x).
149 Easy
149 of 581
Analyzing +4 | -1
The number of values of xx lying in the interval (− π, π)\left( { - \,\mathrm{\pi },\,\mathrm{\pi }} \right) which satisfy the equation
8(1+∣cos⁡x∣+cos⁡2x+∣cos⁡3x∣+...∞)  =43{8^{(1 + |\cos x| + {{\cos }^2}x + |{{\cos }^3}x| + ...\infty )}}\,\, = {4^3}, is
View answer and explanation
Correct option: B
4
Option B (4) is correct because there are four solutions for x in the interval (-π\pi, π\pi) that satisfy the given equation.
150 Easy
150 of 581
Analyzing +4 | -1
The number of solution of tan⁡x+sec⁡x=2cos⁡x\tan x+\sec x=2 \cos x in [0,2π[0,2 \pi ) is
View answer and explanation
Correct option: B
3
The number of solutions is 3 because solving the equation leads to sin⁡x=12\sin x = \frac{1}{2} and sin⁡x=−1\sin x = -1, giving three solutions in the interval [0,2π)[0, 2\pi).
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