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Prove that: 1cosA+sinA-1+1cosA+sinA+1=cosecA+secA - Mathematics

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Question

Prove that:

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

Sum

Solution

L.H.S. = `1/(cosA + sinA - 1) + 1/(cosA + sinA + 1)`

= `(cosA + sinA + 1 + cosA + sinA - 1)/((cosA + sinA)^2 - 1)`

= `(2(cosA + sinA))/(cos^2A + sin^2A + 2cosAsinA - 1)`

= `(2(cosA + sinA))/(1 + 2cosAsinA - 1)`

= `(cosA + sinA)/(cosAsinA)`

= `cosA/(cosAsinA) + sinA/(cosAsinA)`

= `1/sinA + 1/cosA`

= cosec A + sec A = R.H.S.

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Chapter 21: Trigonometrical Identities - Exercise 21 (B) [Page 327]

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Selina Mathematics [English] Class 10 ICSE
Chapter 21 Trigonometrical Identities
Exercise 21 (B) | Q 1.9 | Page 327
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