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Let f(x) = |sin x| .Then...

Let f(x) = |sin x| .Then

A

f is everywhere differentiable

B

f is everywhere continuous but no differentiable at x = n`pi,n epsilon`Z

C

f is everywhere continuous but not differentiable at x=`(2n+1) pi/2,n epsilon Z`

D

None of these

Text Solution

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The correct Answer is:
To solve the problem, we need to analyze the function \( f(x) = |\sin x| \) and determine its properties, particularly its continuity and differentiability. ### Step 1: Understanding the Function The function \( f(x) = |\sin x| \) takes the sine function and applies the absolute value. This means that wherever \( \sin x \) is negative, \( f(x) \) will reflect it to be positive. ### Step 2: Graphing the Function To visualize \( f(x) \), we can sketch the graph of \( \sin x \) and then reflect the negative portions above the x-axis: - The sine function oscillates between -1 and 1. - The points where \( \sin x = 0 \) (i.e., \( x = n\pi \) for \( n \in \mathbb{Z} \)) will remain at 0. - The points where \( \sin x < 0 \) will be reflected to positive values. ### Step 3: Identifying Points of Non-Differentiability The function \( f(x) \) will not be differentiable at points where \( \sin x \) changes from negative to positive, which occurs at: - \( x = n\pi \) for \( n \in \mathbb{Z} \) (where \( \sin x \) crosses the x-axis). At these points, the left-hand derivative and the right-hand derivative will not be equal, indicating non-differentiability. ### Step 4: Conclusion Thus, we conclude that: - The function \( f(x) = |\sin x| \) is continuous everywhere because the sine function is continuous and the absolute value function does not introduce any discontinuities. - The function is not differentiable at \( x = n\pi \) for \( n \in \mathbb{Z} \). ### Summary of Results - **Continuity**: \( f(x) \) is continuous for all \( x \). - **Differentiability**: \( f(x) \) is not differentiable at \( x = n\pi \) for \( n \in \mathbb{Z} \).
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Knowledge Check

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