Question:medium

Prove that the function defined by \(f(x)=\begin{cases}x^2\sin\dfrac1x, & x\neq0\\0, & x=0\end{cases}\) is continuous.

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Away from 0, \(f\) is a product of continuous functions; at 0, squeeze \(x^2\sin(1/x)\) between \(-x^2\) and \(x^2\).
Updated On: Sep 23, 2026
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Solution and Explanation

Step 1: Bounding the absolute value directly:
For \(x\neq0\), \(|f(x)-f(0)|=|x^2\sin(1/x)-0|=x^2|\sin(1/x)|\le x^2\), using \(|\sin(1/x)|\le1\).

Step 2: Epsilon-delta style bound:
Given any \(\epsilon>0\), choosing \(\delta=\sqrt{\epsilon}\) ensures that whenever \(|x-0|<\delta\), \(|f(x)-f(0)|\le x^2<\delta^2=\epsilon\).

Step 3: Concluding:
This is precisely the \(\epsilon\text{-}\delta\) definition of \(\displaystyle\lim_{x\to0}f(x)=f(0)\).

Final Answer:
Hence \(\boxed{f\text{ is continuous at }x=0}\) (and elsewhere, as a product of continuous pieces), matching the Squeeze Theorem approach.
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