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महाराष्ट्र राज्य शिक्षण मंडळएस.एस.सी (इंग्रजी माध्यम) इयत्ता १० वी

Prove that (cot A + cosec A - 1)/(cot A - cosec A + 1) = (1 + cos A)/(sin A).

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प्रश्न

Prove that `(cot A + "cosec"  A - 1)/(cot A - "cosec"  A + 1) = (1 + cos A)/(sin A)`.

सिद्धांत
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उत्तर

L.H.S. = `(cot A + "cosec" A - 1)/(cot A - "cosec" A + 1)`

= `(cot A + "cosec" A - ("cosec"^2A - cot^2A))/(cot A - "cosec" A + 1)`   ...`[(∵ 1 + cot^2A = "cosec"^2A),(∴ "cosec"^2A - cot^2A = 1)]`

= `(cot A + "cosec" A - ("cosec" A + cot A)("cosec" A - cot A))/(cot A - "cosec" A + 1)`   ...[∵ a2 – b2 = (a + b) (a – b)]

= `((cot A + "cosec" A)(1 - "cosec" A + cot A))/(cot A - "cosec" A + 1)`

= cot A + cosec A

= `(cos A)/(sin A) + 1/(sin A)`

= `(cos A + 1)/(sin A)`

= R.H.S.

∴ `(cot A + "cosec" A - 1)/(cot A - "cosec" A + 1) = (1 + cos A)/(sin A)`

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पाठ 6: Trigonometry - Exercise

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