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Prove the Following Identity : Cot a + Cos E C a − 1 Cot a − Cos E C a + 1 = Cos a + 1 Sin a - Mathematics

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प्रश्न

Prove the following identity : 

`(cotA + cosecA - 1)/(cotA - cosecA + 1) = (cosA + 1)/sinA`

योग

उत्तर

`(cotA + cosecA - 1)/(cotA - cosecA + 1) = (cosA + 1)/sinA`

LHS = `(cotA + cosecA - 1)/(cotA - cosecA + 1)`

we know that , cosec2A - cot2A = 1

substituting this in the numerator

`(cosecA + cotA - (cosec^2A - cot^2A))/(cotA - cosecA + 1)`   .....(x²-y²= (x+y)(x-y))

`(cosecA + cotA - (cosecA + cotA)(cosecA - cotA))/(cotA - cosecA + 1)`

taking common 

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

cancelling like terms in numerator and denominator 
we are left with cosec A + cot A

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

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

= RHS

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अध्याय 21: Trigonometric Identities - Exercise 21.1

APPEARS IN

फ्रैंक Mathematics - Part 2 [English] Class 10 ICSE
अध्याय 21 Trigonometric Identities
Exercise 21.1 | Q 2.11
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