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The value of ‘k’ for which the function f(x) = ,,{1-cos4x8x2, ifx≠0k, ifx=0 is continuous at x = 0 is ______.

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Question

The value of ‘k’ for which the function f(x) = `{{:((1 - cos4x)/(8x^2)",",  if x ≠ 0),(k",",  if x = 0):}` is continuous at x = 0 is ______.

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Solution

The value of ‘k’ for which the function f(x) = `{{:((1 - cos4x)/(8x^2)",",  if x ≠ 0),(k",",  if x = 0):}` is continuous at x = 0 is 1.

Explanation:

The function f is continuous at x = 0 if `lim_(x -> 0) f(x) = f(0)`

We have f(0) = k and

`lim_(x -> 0) f(x)` = `lim_(x -> 0) (1 - cos)/(8x^2)`

= `lim_(x -> 0) (2sin^2 2x)/(8x^2)`

= `lim_(x -> 0) (sin^2 2x)/(4x^2)`

= `lim_(x -> 0) ((sin2x)/(2x))^2` = 1

Hence, k = 1

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