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JEE Main 20244 AprilMorning Shift
Exam
JEE Main
Year
2024
Date
4 April
Shift
Morning Shift
Subject
Mathematics
Chapter
Continuity and Differentiability

JEE Main 2024 · 4 April · Morning Shift · Mathematics · Continuity and Differentiability

Let f: R arrow R be a function given by f(x)=\ array ll (1- 2...

Let f:R→Rf: \mathbf{R} \rightarrow \mathbf{R} be a function given by f(x)=\left\{1−cos⁡2xx2,x<0α,x=0,β1−cos⁡xx,x>0\begin{array}{ll} \frac{1-\cos 2 x}{x^2}, & x < 0 \\ \alpha, & x=0, \\ \frac{\beta \sqrt{1-\cos x}}{x}, & x>0 \end{array}\right. where α,β∈R\alpha, \beta \in \mathbf{R}. If ff is continuous at x=0x=0, then α2+β2\alpha^2+\beta^2 is equal to :

Options

  1. A3
  2. B12
  3. C48
  4. D6

Correct answer

B. 12

Step-by-step solution

f(0−)=lim⁡x→0−2sin⁡2xx2=2=αf(0+)=lim⁡x→0+β×2sin⁡x22x2=β2=2⇒β=22α2+β2=4+8=12\begin{aligned} & f\left(0^{-}\right)=\lim _{x \rightarrow 0^{-}} \frac{2 \sin ^2 x}{x^2}=2=\alpha \\ & f\left(0^{+}\right)=\lim _{x \rightarrow 0^{+}} \beta \times \sqrt{2} \frac{\sin \frac{x}{2}}{2 \frac{x}{2}}=\frac{\beta}{\sqrt{2}}=2 \\ & \Rightarrow \beta=2 \sqrt{2} \\ & \alpha^2+\beta^2=4+8=12\end{aligned}
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