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Consider the equation sec theta +cosec...

Consider the equation
`sec theta +cosec theta=a, theta in (0, 2pi) -{pi//2, pi, 3pi//2}`
If the equation has four distinct real roots, then (a) `|a| gt 2sqrt(2)` (b) `|a| lt 2sqrt(2)` (c) `a ge -2sqrt(2)` (d) none of these

A

`|a| gt 2sqrt(2)`

B

`|a| lt 2sqrt(2)`

C

`a ge -2sqrt(2)`

D

none of these

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The correct Answer is:
To solve the equation \( \sec \theta + \csc \theta = a \) for \( \theta \in (0, 2\pi) - \{\frac{\pi}{2}, \pi, \frac{3\pi}{2}\} \), we need to analyze the behavior of the left-hand side of the equation and determine the conditions under which it can have four distinct real roots. ### Step 1: Rewrite the equation We start by rewriting the equation in terms of sine and cosine: \[ \sec \theta = \frac{1}{\cos \theta}, \quad \csc \theta = \frac{1}{\sin \theta} \] Thus, the equation becomes: \[ \frac{1}{\cos \theta} + \frac{1}{\sin \theta} = a \] ### Step 2: Combine the fractions We can combine the fractions on the left-hand side: \[ \frac{\sin \theta + \cos \theta}{\sin \theta \cos \theta} = a \] This leads to: \[ \sin \theta + \cos \theta = a \sin \theta \cos \theta \] ### Step 3: Analyze the function \( f(\theta) = \sin \theta + \cos \theta \) The function \( f(\theta) = \sin \theta + \cos \theta \) can be rewritten using the identity: \[ f(\theta) = \sqrt{2} \sin\left(\theta + \frac{\pi}{4}\right) \] The maximum value of \( f(\theta) \) is \( \sqrt{2} \) and the minimum value is \( -\sqrt{2} \). ### Step 4: Determine the range of \( a \) For the equation \( \sin \theta + \cos \theta = a \sin \theta \cos \theta \) to have four distinct real roots, the value of \( a \) must be such that the right-hand side can take on values in the range of \( f(\theta) \). The product \( \sin \theta \cos \theta \) can be rewritten as: \[ \sin \theta \cos \theta = \frac{1}{2} \sin(2\theta) \] The maximum value of \( \sin(2\theta) \) is 1, so the maximum value of \( \sin \theta \cos \theta \) is \( \frac{1}{2} \). ### Step 5: Set conditions for \( a \) For \( a \sin \theta \cos \theta \) to reach the maximum and minimum values of \( \sin \theta + \cos \theta \): - The maximum value of \( a \cdot \frac{1}{2} \) must be greater than or equal to \( \sqrt{2} \). - The minimum value of \( a \cdot \frac{1}{2} \) must be less than or equal to \( -\sqrt{2} \). Thus, we can set up the inequalities: \[ \frac{a}{2} \geq \sqrt{2} \quad \text{and} \quad \frac{a}{2} \leq -\sqrt{2} \] ### Step 6: Solve the inequalities From \( \frac{a}{2} \geq \sqrt{2} \): \[ a \geq 2\sqrt{2} \] From \( \frac{a}{2} \leq -\sqrt{2} \): \[ a \leq -2\sqrt{2} \] ### Step 7: Conclusion Thus, the conditions for \( a \) imply that \( |a| \) must be greater than \( 2\sqrt{2} \). Therefore, the correct choice is: \[ \text{(a) } |a| > 2\sqrt{2} \]

To solve the equation \( \sec \theta + \csc \theta = a \) for \( \theta \in (0, 2\pi) - \{\frac{\pi}{2}, \pi, \frac{3\pi}{2}\} \), we need to analyze the behavior of the left-hand side of the equation and determine the conditions under which it can have four distinct real roots. ### Step 1: Rewrite the equation We start by rewriting the equation in terms of sine and cosine: \[ \sec \theta = \frac{1}{\cos \theta}, \quad \csc \theta = \frac{1}{\sin \theta} \] Thus, the equation becomes: ...
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CENGAGE ENGLISH-TRIGONOMETRIC EQUATIONS-Exercises (Linked comprehension type)
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  2. Consider the cubic equation x^3-(1+cos theta+sin theta)x^2+(cos theta ...

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  3. Consider the cubic equation x^3-(1+cos theta+sin theta)x^2+(cos theta ...

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  4. Consider the equation sec theta +cosec theta=a, theta in (0, 2pi) -{...

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  5. Consider the equation sec theta +cosec theta=a, theta in (0, 2pi) -{...

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  6. Consider the equation sec theta +cosec theta=a, theta in (0, 2pi) -{...

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  7. Consider the system of equations sin x cos 2y=(a^(2)-1)^(2)+1, cos x...

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  8. Consider the system of equations sin x cos 2y=(a^(2)-1)^(2)+1, cos x...

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  9. Consider the system of equations sin x cos 2y=(a^(2)-1)^(2)+1, cos x...

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  10. Cosider the equation int(0)^(x) (t^(2)-8t+13)dt= x sin (a//x) The nu...

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  11. Cosider the equation int(0)^(x) (t^(2)-8t+13)dt= x sin (a//x) One of...

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  12. Cosider the equation int(0)^(x) (t^(2)-8t+13)dt= x sin (a//x) If x t...

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  13. Consider the system of equations x cos^(3) y+3x cos y sin^(2) y=14 ...

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  14. Consider the system of equations x cos^(3) y+3x cos y sin^(2) y=14 ...

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  15. Consider the system of equations x cos^(3) y+3x cos y sin^(2) y=14 ...

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  16. Let S(1) be the set of all those solution of the equation (1+a) cos th...

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  17. Let S(1) be the set of all those solution of the equation (1+a) cos th...

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  18. All the permissible value of b ,a=sin(2x-b)if a=0 and x=S(2) is a subs...

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  19. For what values of 'b' does the equation ( b cos x)/( 2 cos 2x -1) =( ...

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