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JEE Main 202325 JanuaryEvening Shift
Exam
JEE Main
Year
2023
Date
25 January
Shift
Evening Shift
Subject
Mathematics
Chapter
Continuity and Differentiability

JEE Main 2023 · 25 January · Evening Shift · Mathematics · Continuity and Differentiability

If the function f(x) = \ cases (1 + | x |)(λ)/(| x |), & 0

If the function f\left(x\right) = \left\{\begin{cases}\left(1 + | \cos x |\right)\dfrac{\lambda}{| \cos x |}, & 0 < x < \dfrac{\pi}{2} \\ \mu, & x = \dfrac{\pi}{2} \\ e\dfrac{\cot 6x}{\cot 4x}, & \dfrac{\pi}{2} < x < \pi\end{cases}\right)is continuous atx = \dfrac{\pi}{2},then, then9\lambda + 6\log_{c}\mu + {\mu}^{6} - {e}^{6\lambda} is equal to

Options

  1. A1111
  2. B88
  3. C2e4+82{e}^{4} + 8
  4. D1010

Correct answer

D. 1010

Step-by-step solution

Given,

f(x)f\left(x\right) is continuous at x=π2x = \dfrac{\pi}{2}

Now, solving L.H.L.L . H . L . at x=π2x = \dfrac{\pi}{2} we get,

lim⁡x→π+2ecot⁡6xcot⁡4x=lim⁡x→π+2esin⁡4x⋅cos⁡6xsin⁡6x⋅cos⁡4x=e2/3\lim_{x \to \dfrac{{\pi}^{+}}{2}}e\dfrac{\cot 6x}{\cot 4x} = \lim_{x \to \dfrac{{\pi}^{+}}{2}}e\dfrac{\sin 4x \cdot \cos 6x}{\sin 6x \cdot \cos 4x} = {e}^{2 / 3}

Similarly, on simplification for R.H.L.R . H . L . we get

lim⁡x→π2−(1+∣cos⁡x∣)λ∣cos⁡x∣=elim⁡x→π2−λ=eλ\lim_{x \to \dfrac{\pi}{2} -}\left(1 + | \cos x |\right)\dfrac{\lambda}{| \cos x |} = {e}^{\lim_{x \to \dfrac{\pi}{2} -}\lambda} = {e}^{\lambda}

∵f(π2)=μ∵ f\left(\dfrac{\pi}{2}\right) = \mu

For continuous function,

f(π2−)=f(π2)=f(π2+)f\left(\dfrac{\pi}{2} -\right) = f\left(\dfrac{\pi}{2}\right) = f\left(\dfrac{\pi}{2} +\right)

⇒e23=eλ=μ⇒ e\dfrac{2}{3} = {e}^{\lambda} = \mu

⇒λ=23,μ=e23⇒ \lambda = \dfrac{2}{3}, \mu = e\dfrac{2}{3}

Now,

9λ+6log⁡eμ+μ6−e6λ9\lambda + 6\log_{e}\mu + {\mu}^{6} - {e}^{6\lambda}

=9(23)+6(23)+(e23)6−e6(23)= 9 ( \dfrac{2}{3} ) + 6 ( \dfrac{2}{3} ) + {\left(e\dfrac{2}{3}\right)}^{6} - {e}^{6 ( \dfrac{2}{3} )}

=6+4+e4−e4= 6 + 4 + {e}^{4} - {e}^{4}

=10= 10

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