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Prove the following identities: (cosec theta + cot theta)/(cosec theta – cot theta) = (cosec theta + cot theta)^2 = 1 + 2 cot^2 theta + 2 cosec theta cot theta

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Question

Prove the following identities:

`("cosec"  theta + cot theta)/("cosec"  theta - cot theta) = ("cosec"  theta + cot theta )^2 = 1 + 2 cot^2 theta + 2  "cosec"  theta cot theta`

Theorem
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Solution

Here, `( cosec theta + cot theta )/( cosec theta - cot theta)`

        = `((cosec theta + cot theta) ( cosec theta + cot theta ))/(( cosec theta - cot theta ) ( cosec theta + cot theta))`

        =` ((cosec theta + cot theta)^2)/(( cosec ^2 theta - cot^2 theta))`

       =`((cosec theta + cot theta )^2) /1`

      =`(cosec theta + cot theta )^2`

 Again , `( cosec theta + cot theta )^2`

     = ` cosec^2 theta + cot^2 theta + 2 cosec theta  cot theta `

     =` 1+cot^2 theta + cot^2 theta + 2 cosec theta  cot theta (∵ cosec^2 theta - cot^2 theta =1)`

    =` 1+2 cot^2 theta + 2 cosec theta  cot theta `

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Chapter 13: Trigonometric identities - EXERCISE 13A [Page 618]

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R.S. Aggarwal Mathematics [English] Class 10
Chapter 13 Trigonometric identities
EXERCISE 13A | Q 24. | Page 618

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