Continuity and Differentiability of |x|

Rarely Tested

$$f(x) = |x|$$ is continuous everywhere but not differentiable at $$x=0$$:
  • LHD = -1, RHD = 1
  • Discontinuity in derivative
Question 1

Consider the function $$f:\left(-\tfrac{\pi}{2},\tfrac{\pi}{2}\right)\to(-\infty,\infty)$$ defined by

$$f(x)=(|x|+|x-1|)\sin x+[x\sin x],$$

where $$[x\sin x]$$ is the greatest integer less than or equal to $$x\sin x$$.

Let $$\alpha$$ be the total number of points in the interval $$\left(-\tfrac{\pi}{2},\tfrac{\pi}{2}\right)$$ at which $$f$$ is NOT continuous, and let $$\beta$$ be the total number of points in the interval $$\left(-\tfrac{\pi}{2},\tfrac{\pi}{2}\right)$$ at which $$f$$ is NOT differentiable. Then the value of $$\alpha+\beta$$ is ___.

Question 2

Let $$f(x)=\max\left\{|x^2-2x|,\frac{x}{2}\right\}$$ for $$x\in[0,3]$$

Find the sum of all values of $$x\in(0,3)$$ where $$f(x)$$ is continuous but not differentiable.

Go back to topics

Join CAT 2026 course by 5-Time CAT 100%iler

Start your IIM journey with the right preparation and crack CAT 2026.