हिंदी

Prove that (cot A)/(1 – cot A) + (tan A)/(1 – tan A) = –1.

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प्रश्न

Prove that `(cot A)/(1 - cot A) + (tan A)/(1 - tan A) = -1`.

प्रमेय
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उत्तर

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

= `(cot A)/(1 - 1/(tan A)) + (tan A)/(1 - tan A)`

= `(cot A)/((tan A - 1)/(tan A)) + (tan A)/(1 - tan A)`

= `(cot A tan A)/(tan A - 1) + (tan A)/(1 - tan A)`

= `1/(tan A - 1) + (tan A)/(1 - tan A)`   ...[∵ cot A tan A = 1]

= `- 1/(1 - tan A) + (tan A)/(1 - tan A)`

= `- (1/(1 - tan A) - (tan A)/(1 - tan A))`

= `-((1 - tan A)/(1 - tan A))`

= –1

= R.H.S.

∴ `(cot A)/(1 - cot A) + (tan A)/(1 - tan A) = -1`

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