Verified Solution • 2025–26 Session moderate

QJEEM13Ma4d12: JEE Main 2013 Mathematics - Class 12 JEEM13Ma4d12 Solution

lim⁡x→0(1−cos⁡2x)(3+cos⁡x)xtan⁡4x\mathop {\lim }\limits_{x \to 0} {{\left( {1 - \cos 2x} \right)\left( {3 + \cos x} \right)} \over {x\tan 4x}} is equal to

Multiple Choice Options

  • A −14- {1 \over 4}
  • B 12{1 \over 2}
  • C 1
  • D 2

Step-by-Step Verified Solution

Multiply and divide by xx in the given expression, we get

lim⁡x→0(1−cos⁡2x)x2(3+cos⁡x)1.xtan⁡ 4x\mathop {\lim }\limits_{x \to 0} {{\left( {1 - \cos 2x} \right)} \over {{x_2}}}{{\left( {3 + \cos x} \right)} \over 1}.{x \over {\tan \,4x}}

=lim⁡x→02sin⁡2xx2.3+cos⁡x1.xtan⁡4x= \mathop {\lim }\limits_{x \to 0} {{2{{\sin }^2}x} \over {{x^2}}}.{{3 + \cos x} \over 1}.{x \over {\tan 4x}}

=2lim⁡x→0sin⁡2xx2.lim⁡x→03+cos⁡x.lim⁡x→0xtan⁡4x= 2\mathop {\lim }\limits_{x \to 0} {{{{\sin }^2}x} \over {{x^2}}}.\mathop {\lim }\limits_{x \to 0} 3 + \cos x.\mathop {\lim }\limits_{x \to 0} {x \over {\tan 4x}}

=2.414lim⁡x→04xtan⁡4x=2.4.14=2= 2.4{1 \over 4}\mathop {\lim }\limits_{x \to 0} {{4x} \over {\tan 4x}} = 2.4.{1 \over 4} = 2

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