JEE Advanced · Mathematics · 8. Trigonometric Equations
The number of all possible values of \(\theta\), where \(0 < \theta < \pi\), for which the system of equations
\((y+z) \cos 3 \theta=(x y z) \sin 3 \theta \) \( x \sin 3 \theta=\frac{2 \cos 3 \theta}{y}+\frac{2 \sin 3 \theta}{z}\) and \((x y z) \sin 3 \theta=(y+2 z) \cos 3 \theta\) \(+y \sin 3 \theta\) have a solution \(\left(x_0, y_0, z_0\right)\) with \(\quad y_0 z_0 \neq 0\), is
- A 1
- B 6
- C 7
- D 3
Answer & Solution
Correct Answer
(D) 3
Step-by-step Solution
Detailed explanation
Given equations can be written as
\(x \sin 3 \theta-\frac{\cos 3 \theta}{y}-\frac{\cos 3 \theta}{z}=0 \)
\( x \sin 3 \theta-\frac{2 \cos 3 \theta}{y}-\frac{2 \sin 3 \theta}{z}=0 \)
\( \text { and } x \sin 3 \theta-\frac{2}{y} \cos 3 \theta \)
\( -\frac{1}{z}(\cos 3 \theta+\sin 3 \theta)=0\)
Eqs. (ii) and (iii), implies
\(2 \sin 3 \theta=\cos 3 \theta+\sin 3 \theta \)
\( \Rightarrow \sin 3 \theta=\cos 3 \theta \)
\( \therefore \tan 3 \theta=1 \)
\( \Rightarrow 3 \theta=\frac{\pi}{4}, \frac{5 \pi}{4}, \frac{9 \pi}{4} \text { or } \theta=\frac{\pi}{12}, \frac{5 \pi}{12}, \frac{9 \pi}{12}.\)
\(x \sin 3 \theta-\frac{\cos 3 \theta}{y}-\frac{\cos 3 \theta}{z}=0 \)
\( x \sin 3 \theta-\frac{2 \cos 3 \theta}{y}-\frac{2 \sin 3 \theta}{z}=0 \)
\( \text { and } x \sin 3 \theta-\frac{2}{y} \cos 3 \theta \)
\( -\frac{1}{z}(\cos 3 \theta+\sin 3 \theta)=0\)
Eqs. (ii) and (iii), implies
\(2 \sin 3 \theta=\cos 3 \theta+\sin 3 \theta \)
\( \Rightarrow \sin 3 \theta=\cos 3 \theta \)
\( \therefore \tan 3 \theta=1 \)
\( \Rightarrow 3 \theta=\frac{\pi}{4}, \frac{5 \pi}{4}, \frac{9 \pi}{4} \text { or } \theta=\frac{\pi}{12}, \frac{5 \pi}{12}, \frac{9 \pi}{12}.\)
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Mathematics
- Let be two non-constant differentiable functions. If , and then which of the following statement(s) is (are) TRUE?JEE Advanced 2018 Medium
- Paragraph:
Let \(p\) be an odd prime number and \(T_p\) be the following set of \(2 \times 2\) matrices
\[
T_p=\left\{A=\left[\begin{array}{ll}
a & b \\
c & a
\end{array}\right] ; a, b, c \in\{0,1,2, \ldots, p-1\}\right\}
\]Question:
The number of \(A\) in \(T_p\) such that \(\operatorname{det}(A)\) is not divisible by \(p\), isJEE Advanced 2010 Easy - Match the following
JEE Advanced 2006 Medium - Let and be two unit vectors such that For some let If and the vector is inclined at the same angle to both and then the value of isJEE Advanced 2018 Medium
- Paragraph: Let be the circle in the – plane defined by the equation
Question : Let be a point on the circle with both coordinates being positive. Let the tangent to at intersect the coordinate axes at the points and Then, the mid-point of the line segment must lie on the curveJEE Advanced 2018 Medium - Let and be real numbers such that and . If the complex number satisfies then which of the following is (are) possible value (s) ofJEE Advanced 2017 Medium
More PYQs from JEE Advanced
- An ideal gas undergoes a four step cycle as shown in the diagram below. During this cycle, heat is absorbed by the gas in:
JEE Advanced 2021 Medium - The tangent \(P T\) and the normal \(P N\) to the parabola \(y^2=4 a x\) at a point \(P\) onJEE Advanced 2009 Medium
- The correct stability order for the following species is
JEE Advanced 2008 Medium - The total number(s) of stable conformers with non-zero dipole moment for the following compound is(are)
JEE Advanced 2014 Hard - A ray of light travelling in water is incident on its surface open to air. The angle of incidence is \(\theta\), which is less than the critical angle. Then there will beJEE Advanced 2007 Medium
- For the given close packed structure of a salt made of cation and anion shown below (ions of only one face are shown for clarity), the packing fraction is approximately (packing fraction )
JEE Advanced 2021 Medium