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If F ( X ) = ( 1 − Cos X X 2 , X ≠ 0 K , X = 0 ) is Continuous at X = 0, Find K. - Mathematics

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Question

If  \[f\left( x \right) = \binom{\frac{1 - \cos x}{x^2}, x \neq 0}{k, x = 0}\]  is continuous at x = 0, find k

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Solution

Given: 

\[f\left( x \right) = \binom{\frac{1 - \cos x}{x^2}, x \neq 0}{k, x = 0}\]

If  \[f\left( x \right)\]  is continuous at  \[x = 0\] , then

\[\lim_{x \to 0} f\left( x \right) = f\left( 0 \right)\]

\[\Rightarrow \lim_{x \to 0} \left( \frac{1 - \cos x}{x^2} \right) = k\]
\[ \Rightarrow \lim_{x \to 0} \left( \frac{2 \left[ \sin \left( \frac{x}{2} \right) \right]^2}{4 \left( \frac{x}{2} \right)^2} \right) = k\]
\[ \Rightarrow \frac{1}{2} \lim_{x \to 0} \left( \frac{\left[ \sin\left( \frac{x}{2} \right) \right]^2}{\left( \frac{x}{2} \right)^2} \right) = k\]
\[ \Rightarrow 1 \times \frac{1}{2} = k\]
\[ \Rightarrow k = \frac{1}{2}\]
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Chapter 9: Continuity - Exercise 9.3 [Page 42]

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RD Sharma Mathematics [English] Class 12
Chapter 9 Continuity
Exercise 9.3 | Q 8 | Page 42

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