Q2 / 93 · NTA Abhyas (JEE Main) 2020 · Mathematics · Continuity and Differentiability

Let fx=1+cosxπ−x2⋅sin2xln1+π2−2πx+x2 x≠πλ x=π is continuous at x=π, then λ is equal to

  • A
    1
  • B
    -1
  • Correct answer
    C
    12
  • D
    14

Solution

For fx to be continuous at x=π,
limx→π⁡fx=fπ
Now, limx→π⁡1+cos⁡xπ-x2·sin2⁡xln⁡1+π-x2=λ
Putting x=π+t, we get,
∴ lim t→0 1−cost t 2 ⋅ sin 2 t ln 1+ t 2 =λ
lim t→0 1 2 ⋅ sin 2 t t 2 ⋅ t 2 ln 1+ t 2 =λ
12×1×1=λ⇒λ=12

Hence, the correct answer is option: 'C'.

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