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1 + Cos X 1 − Cos X is Equal to

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Question

\[\sqrt{\frac{1 + \cos x}{1 - \cos x}}\] is equal to

 

Options

  • cosec x + cot x

  • cosec x − cot x

  • −cosec x + cot x

  • −cosec x − cot x

MCQ
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Solution

−cosec x − cot x
\[\sqrt{\frac{1 + \cos x}{1 - \cos x}} \]
\[ = \sqrt{\frac{\left( 1 + \cos x \right)\left( 1 + \cos x \right)}{\left( 1 - \cos x \right)\left( 1 + \cos x \right)}}\]
\[ = \sqrt{\frac{\left( 1 + \cos x \right)^2}{1 - \cos^2 x}}\]
\[ = \sqrt{\frac{\left( 1 + \cos x \right)^2}{\sin^2 x}}\]
\[ = \frac{\left( 1 + \cos x \right)}{- \sin x} \left[\text{ as, }\pi < x < 2\pi,\text{ so }\sin x\text{ will be negative }\right]\]
\[ = - \left( cosec x + \cot x \right) \]
\[ = - cosec x - \cot x\]

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Chapter 5: Trigonometric Functions - Exercise 5.5 [Page 41]

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R.D. Sharma Mathematics [English] Class 11
Chapter 5 Trigonometric Functions
Exercise 5.5 | Q 4 | Page 41

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