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Evaluate the following limit : limx→π6[2-cosecxcot2x-3]

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Question

Evaluate the following limit :

`lim_(x -> pi/6) [(2 - "cosec"x)/(cot^2x - 3)]`

Sum
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Solution

`lim_(x -> pi/6) [(2 - "cosec"x)/(cot^2x - 3)]`

= `lim_(x -> pi/6) (2 - "cosec"x)/("cosec"^2x - 1 - 3)`

= `lim_(x -> pi/6) (2 - "cosec"x)/("cosec"^2x - 4)`

= `lim_(x -> pi/6) (-("cosec"x - 2))/(("cosec"x - 2)("cosec"x + 2))`

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

= `(-1)/("cosec"(pi/6) + 2)`

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

= `(-1)/4`

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Chapter 7: Limits - Exercise 7.4 [Page 148]

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