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If -pi lt theta lt -(pi)/(2)," then " |...

If `-pi lt theta lt -(pi)/(2)," then " |sqrt((1-sin theta)/(1+sintheta))+sqrt((1+sin theta)/(1-sin theta))|` is equal to :

A

` 2 sec theta`

B

` -2 sec theta`

C

`2"sec"(theta)/(2)`

D

`-"sec"(theta)/(2)`

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The correct Answer is:
To solve the problem, we need to evaluate the expression \[ \left| \sqrt{\frac{1 - \sin \theta}{1 + \sin \theta}} + \sqrt{\frac{1 + \sin \theta}{1 - \sin \theta}} \right| \] for the range \(-\pi < \theta < -\frac{\pi}{2}\). ### Step 1: Write the expression We start with the expression: \[ E = \sqrt{\frac{1 - \sin \theta}{1 + \sin \theta}} + \sqrt{\frac{1 + \sin \theta}{1 - \sin \theta}} \] ### Step 2: Find a common denominator To combine the two square root terms, we find a common denominator: \[ E = \frac{\sqrt{(1 - \sin \theta)^2} + \sqrt{(1 + \sin \theta)^2}}{\sqrt{(1 + \sin \theta)(1 - \sin \theta)}} \] ### Step 3: Simplify the numerator The numerator simplifies to: \[ \sqrt{(1 - \sin \theta)^2} + \sqrt{(1 + \sin \theta)^2} = |1 - \sin \theta| + |1 + \sin \theta| \] ### Step 4: Simplify the denominator The denominator can be simplified using the identity \(1 - \sin^2 \theta = \cos^2 \theta\): \[ \sqrt{(1 + \sin \theta)(1 - \sin \theta)} = \sqrt{1 - \sin^2 \theta} = \cos \theta \] ### Step 5: Substitute back into the expression Now we can rewrite \(E\): \[ E = \frac{|1 - \sin \theta| + |1 + \sin \theta|}{\cos \theta} \] ### Step 6: Determine the signs of the terms For \(-\pi < \theta < -\frac{\pi}{2}\), we know that \(\sin \theta\) is negative. Therefore: - \(1 - \sin \theta\) is positive (since \(\sin \theta < 0\)) - \(1 + \sin \theta\) is also positive (since \(\sin \theta > -1\)) Thus, we can drop the absolute values: \[ E = \frac{(1 - \sin \theta) + (1 + \sin \theta)}{\cos \theta} = \frac{2}{\cos \theta} \] ### Step 7: Final expression Now we have: \[ E = \frac{2}{\cos \theta} \] ### Step 8: Apply the modulus Since \(\cos \theta\) is negative in this range, we take the modulus: \[ |E| = \left| \frac{2}{\cos \theta} \right| = -\frac{2}{\cos \theta} \] ### Step 9: Final result Thus, the final expression simplifies to: \[ |E| = -\frac{2}{\cos \theta} \] ### Step 10: Relate to sine Using the identity \(\cos \theta = -\sin\theta\) in this range, we get: \[ |E| = -\frac{2}{-\sin \theta} = \frac{2}{\sin \theta} \] ### Conclusion So, the final answer is: \[ |E| = -2 \sin \theta \]
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