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QJEEM22Maeb37: JEE Main 2022 Mathematics - Class 12 JEEM22Maeb37 Solution: Let f(x) = min {1, 1 + x sin x}, 0 x 2 . If m is the number of…

Let f(x) = min {1, 1 + x sin x}, 0 ≤\le x ≤\le 2 π\pi . If m is the number of points, where f is not differentiable and n is the number of points, where f is not continuous, then the ordered pair (m, n) is equal to

Multiple Choice Options

  • A (2, 0)
  • B (1, 0)
  • C (1, 1)
  • D (2, 1)

Step-by-Step Verified Solution

f(x)=min⁡{1, 1+xsin⁡x}f(x) = \min \{ 1,\,1 + x\sin x\} , 0≤x≤x0 \le x \le x

f(x)={1,0≤x<π1+xsin⁡x,π≤x≤2π

Now at x=π,  lim⁡x→π−f(x)=1=lim⁡x→π+f(x)x = \pi ,\,\,\mathop {\lim }\limits_{x \to {\pi ^ - }} f(x) = 1 = \mathop {\lim }\limits_{x \to {\pi ^ + }} f(x)

∴\therefore f(x) is continuous in [0, 2 π\pi ]

Now, at x = π\pi L.H.D=lim⁡h→0f(π−h)−f(π)−h=0L.H.D = \mathop {\lim }\limits_{h \to 0} {{f(\pi - h) - f(\pi )} \over { - h}} = 0

R.H.D=lim⁡h→0f(π+h)−f(π)h=1−(π+h)sin⁡ h−1h=−πR.H.D = \mathop {\lim }\limits_{h \to 0} {{f(\pi + h) - f(\pi )} \over h} = 1 - {{(\pi + h)\sin \,h - 1} \over h} = - \pi

∴\therefore f(x) is not differentiable at x = π\pi

∴\therefore (m, n) = (1, 0)

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