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Select the correct answer from the given alternatives. limx→π3(tan2x-3sec3 x-8) =

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Question

Select the correct answer from the given alternatives.

`lim_(x → π/3) ((tan^2x - 3)/(sec^3x - 8))` =

Options

  • 1

  • `1/2`

  • `1/3`

  • `1/4`

MCQ
Sum
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Solution

`lim_(x → π/3) ((tan^2x - 3)/(sec^3x - 8)) = 1/3`

Explanation:

`lim_(x → π/3) ((tan^2x - 3)/(sec^3x - 8))`

`= lim_(x → π/3) ((sec^2x - 1 - 3)/(sec^3x - 8))       ...[(tan^2 x + 1 = sec^2 x),(∵ tan^2 x = sec^2x - 1)]`

`= lim_(x → π/3) ((sec^2x - 4)/(sec^3x - 8))`

`= lim_(x → π/3) ((sec^2x - (2)^2)/(sec^3x - (2)^3))`

`= lim_(x → π/3) ((secx - 2)(secx + 2))/((sec x - 2)(sec^2 x + 2sec x + 4))  ...[(a^2 - b^2 = (a - b)(a + b)),(a^3 - b^3 = (a - b)(a^2 + ab + b^2))]`

`= lim_(x → π/3) (secx + 2)/(sec^2 x + 2sec x + 4)`

`= (sec  π/3 + 2)/((sec  π/3)^2 + 2sec  π/3 + 4)`

`= (2 + 2)/((2)^2 + 2(2) + 4)`

`= 1/3`

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Chapter 7: Limits - Miscellaneous Exercise 7.1 [Page 158]

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