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Prove the following trigonometric identities. sec A (1 − sin A) (sec A + tan A) = 1 - Mathematics

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प्रश्न

Prove the following trigonometric identities.

sec A (1 − sin A) (sec A + tan A) = 1

योग
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उत्तर

We have to prove sec A(1 − sin A)(sec A + tan A) = 1

We know that sec2 A − tan2 A − 1 

So,

sec A(1 − sin A)(sec A + tan A) = {sec A(1 − sin A)}(sec A + tan A)

= (sec A − sec A sin A)(sec A + tan A)

= `(sec A - 1/cos A  sin A) (sec A + tan A)`     ...`(∵ sec theta = 1/costheta)`

= `(sec A - sin A/cos A) (sec A + tan A)`    ...`(∵ tan theta = sin theta/costheta)`

= (sec A − tan A)(sec A + tan A)

= sec2 A − tan2 A

= 1 = R.H.S.    ... (∵ sec2 θ = 1 tan2 θ)

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अध्याय 11: Trigonometric Identities - Exercise 11.1 [पृष्ठ ४४]

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