MCQ
Let $\text{f}(\text{x})=\text{x}-[\text{x}],\text{x}\in\text{R},$ then $\text{f}'\Big(\frac{1}{2}\Big)$ is:
  • A
    $\frac{3}{2}$
  • $1$
  • C
    $0$
  • D
    $-1$

Answer

Correct option: B.
$1$
Given: $\text{f}(\text{x})=\text{x}-[\text{x}],\text{x}\in\text{R}$
Now,
For $0\le\text{x}<1,[\text{x}]=0$
$\therefore\text{f}(\text{x})=\text{x}-0=\text{x},\forall\text{x}\in[0,1)$
Differentiate with respect to $x,$ we get
$\text{f}'(\text{x})=1,\forall\text{x}\in[0,1)$
$\therefore\text{f}'\Big(\frac{1}{2}\Big)=1$

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