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Prove the following identities: (sec theta + tan theta)/(sec theta – tan theta) = (sec theta + tan theta)^2 = 1 + 2 tan^2 theta + 2 sec theta tan theta

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Question

Prove the following identities:

`(sec theta + tan theta)/(sec theta - tan theta) = (sec theta + tan theta)^2 = 1 + 2 tan^2 theta + 2 sec theta tan theta`

Theorem
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Solution

Here, `(sec theta + tan theta ) /( sec theta - tan theta)`

      =`((sec theta + tan theta ) ( sec theta + tan theta))/(( sec theta - tan theta ) ( sec theta + tan theta ))`

      =` ((sec theta + tan theta )^2) /( sec^2 theta - tan^2 theta)`

      =`((sec theta + tan theta )^2)/1`

      =`(sec theta + tan theta )^2`

 Again , `(sec theta + tan theta )2`

      =` sec^2 theta + tan^2 theta + 2 sec theta  tan theta `

      =` 1+ tan^2 theta + tan^2 theta + 2 sec theta tan theta`

      =`1+2 tan^2 theta + 2 sec theta tan 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 25. | Page 618
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