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Evaluate the following limit : limx→π6[2sin2x+sinx-12sin2x-3sinx+1]

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Question

Evaluate the following limit :

`lim_(x -> pi/6) [(2sin^2x + sinx - 1)/(2sin^2x - 3sinx + 1)]`

Sum
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Solution

`lim_(x -> pi/6) (2sin^2x + sinx - 1)/(2sin^2x - 3sinx + 1)`

= `lim_(x -> pi/6) ((2sinx - 1)(sin x + 1))/((2sin x - 1)(sin x - 1))`

= `lim_(x -> pi/6) (sinx + 1)/(sin x - 1)   ...[(because x -> pi/6","  x ≠ pi/6),(therefore sin x ≠ sin  pi/6 = 1/2),(therefore 2 sin x - 1 ≠ 0)]`

= `(lim_(x -> pi/6) (sin x + 1))/(lim_(x -> pi/6) (sin x - 1))`

= `(sin  pi/6 + 1)/(sin  pi/6 - 1)`

= `(1/2 + 1)/(1/2 - 1)`

= `(1 + 2)/(1 - 2)`

= – 3

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Chapter 7: Limits - Exercise 7.4 [Page 148]

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