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Question: Answered & Verified by Expert
Let $\mathrm{f}(\mathrm{x})=[\mathrm{x}]$, where $[.]$ is the greatest integer function and $\mathrm{g}(\mathrm{x})=\sin \mathrm{x}$ be two real valued functions over R.
Which of the following statements is correct?
MathematicsContinuity and DifferentiabilityNDANDA 2016 (Phase 2)
Options:
  • A $\operatorname{Both} \mathrm{f}(\mathrm{x})$ and $\mathrm{g}(\mathrm{x})$ are continuous at $\mathrm{x}=0$.
  • B $\mathrm{f}(\mathrm{x})$ is continuous at $\mathrm{x}=0$, but $\mathrm{g}(\mathrm{x})$ is not continuous at $\mathrm{x}=0 .$
  • C $\mathrm{g}(\mathrm{x})$ is continuous at $\mathrm{x}=0$, but $\mathrm{f}(\mathrm{x})$ is not continuous at $\mathrm{x}=0 .$
  • D Both $\mathrm{f}(\mathrm{x})$ and $\mathrm{g}(\mathrm{x})$ are discontinuous at $\mathrm{x}=0$.
Solution:
1879 Upvotes Verified Answer
The correct answer is: $\mathrm{g}(\mathrm{x})$ is continuous at $\mathrm{x}=0$, but $\mathrm{f}(\mathrm{x})$ is not continuous at $\mathrm{x}=0 .$
$f(x)=[x]$ and $g(x)=\sin x$ $\lim _{x \rightarrow 0^{+}} f(x)=[0+h]=0$
$\lim _{x \rightarrow 0^{-}} f(x)=[0-h]=-1$
$f(0)=0$
$\Rightarrow f(x)$ is not continuous at $x=0$ and also $g(x)$ is
continuous at $x=0$. (every trignometric function is continuous).

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