Verified Solution • 2025–26 Session moderate

QJEEM22Mac754: JEE Main 2022 Mathematics - Class 12 JEEM22Mac754 Solution: If the function f ( x ) = { log e ( 1 − x + x 2 ) + log e ( 1 + …

If the function f(x)={loge(1−x+x2)+loge(1+x+x2)sec⁡x−cos⁡x,x∈(−π2,π2)−{0}k,x=0 is continuous at x = 0, then k is equal to:

Multiple Choice Options

  • A 1
  • B −- 1
  • C e
  • D 0

Step-by-Step Verified Solution

f(x)={loge(1−x+x2)+loge(1+x+x2)sec⁡x−cos⁡x,x∈(−π2,π2)−{0}k,x=0

for continuity at x=0x = 0

lim⁡x→0f(x)=k\mathop {\lim }\limits_{x \to 0} f(x) = k

∴\therefore k=lim⁡x→0log⁡e(x4+x2+1)sec⁡x−cos⁡x(00 form)k = \mathop {\lim }\limits_{x \to 0} {{{{\log }_e}({x^4} + {x^2} + 1)} \over {\sec x - \cos x}}\left( {{0 \over 0}\,\mathrm{form}} \right)

=lim⁡x→0cos⁡xlog⁡e(x4+x2+1)sin⁡2x= \mathop {\lim }\limits_{x \to 0} {{\cos x{{\log }_e}({x^4} + {x^2} + 1)} \over {{{\sin }^2}x}}

=lim⁡x→0log⁡e(x4+x2+1)x2= \mathop {\lim }\limits_{x \to 0} {{{{\log }_e}({x^4} + {x^2} + 1)} \over {{x^2}}}

=lim⁡x→0ln⁡(1+x2+x4)x2+x4 . x2+x4x2= \mathop {\lim }\limits_{x \to 0} {{\ln (1 + {x^2} + {x^4})} \over {{x^2} + {x^4}}}\,.\,{{{x^2} + {x^4}} \over {{x^2}}}

=1= 1

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