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QJEEM19Mad127: JEE Main 2019 Mathematics - Class 12 JEEM19Mad127 Solution: The value of the integral (where [x] denotes the greatest…

The value of the integral ∫−22sin⁡2x[xπ]+12 dx\int\limits_{ - 2}^2 {{{{{\sin }^2}x} \over { \left[ {{x \over \pi }} \right] + {1 \over 2}}}} \,dx (where [x] denotes the greatest integer less than or equal to x) is

Multiple Choice Options

  • A 0
  • B 4
  • C 4 −- sin 4
  • D sin 4

Step-by-Step Verified Solution

I == ∫−22sin⁡2x[xπ]+12 dx\int\limits_{ - 2}^2 {{{{{\sin }^2}x} \over { \left[ {{x \over \pi }} \right] + {1 \over 2}}}} \,dx

I=∫02(sin⁡2x[xπ]+12+sin⁡2(−x)[−xπ]+12)dx{\rm I} = \int\limits_0^2 {\left( {{{{{\sin }^2}x} \over {\left[ {{x \over \pi }} \right] + {1 \over 2}}} + {{{{\sin }^2}\left( { - x} \right)} \over {\left[ { - {x \over \pi }} \right] + {1 \over 2}}}} \right)dx}

([xπ]+[−xπ]=−1  \left( {\left[ {{x \over \pi }} \right] + \left[ { - {x \over \pi }} \right] = - 1\,\,} \right.    as   x≠nπ)

I=∫02(sin⁡2x[xπ]+12+sin⁡2x−1−[xπ]+12)dx=0{\rm I} = \int\limits_0^2 {\left( {{{{{\sin }^2}x} \over {\left[ {{x \over \pi }} \right] + {1 \over 2}}} + {{{{\sin }^2}x} \over { - 1 - \left[ {{x \over \pi }} \right] + {1 \over 2}}}} \right)dx = 0}

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