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JEE Main 202312 AprilMorning Shift
Exam
JEE Main
Year
2023
Date
12 April
Shift
Morning Shift
Subject
Mathematics
Chapter
Application of Derivatives

JEE Main 2023 · 12 April · Morning Shift · Mathematics · Application of Derivatives

If the total maximum value of the function f(x) = ( 3e 2 x ) ^ ^ 2...

If the total maximum value of the function f(x)=(3e2sin⁡x)sin⁡2x,x∈(0,π2),f\left(x\right) = {\left(\dfrac{\sqrt{3e}}{2\sin x}\right)}^{\sin^{2}x}, x \in \left(0, \dfrac{\pi}{2}\right), is ke,\dfrac{k}{e}, then (ke)8+k8e5+k8{\left(\dfrac{k}{e}\right)}^{8} + \dfrac{{k}^{8}}{{e}^{5}} + {k}^{8} is equal to

Options

  1. Ae3+e6+e11{e}^{3} + {e}^{6} + {e}^{11}
  2. Be5+e6+e11{e}^{5} + {e}^{6} + {e}^{11}
  3. Ce3+e6+e10{e}^{3} + {e}^{6} + {e}^{10}
  4. De3+e5+e11{e}^{3} + {e}^{5} + {e}^{11}

Correct answer

A. e3+e6+e11{e}^{3} + {e}^{6} + {e}^{11}

Step-by-step solution

Given function is f(x)=(3e2sin⁡x)sin⁡2xf\left(x\right) = {\left(\dfrac{\sqrt{3}e}{2\sin x}\right)}^{\sin^{2}x}

For maxima or minima f′(x)=0{f}^{'} ( x ) = 0

f′(x)=f(x)[2sin⁡xcos⁡x×ln⁡(3e2sin⁡x)+sin⁡2x1×2sin⁡x3e×3e2(−1sin⁡2x×cos⁡x)]{f}^{'}\left(x\right) = f\left(x\right)\left[2\sin x \cos x \times \ln \left(\dfrac{\sqrt{3}e}{2\sin x}\right) + \sin^{2}x\dfrac{1 \times 2\sin x}{\sqrt{3}e} \times \dfrac{\sqrt{3}e}{2}\left(- \dfrac{1}{\sin^{2}x} \times \cos x\right)\right]

⇒f(x)[sin⁡2xln(3e2sin⁡x)−sin⁡xcos⁡x]=0⇒ f\left(x\right)\left[\sin 2xln\left(\dfrac{\sqrt{3}e}{2\sin x}\right) - \sin x \cos x\right] = 0

Now on equation we get, sin⁡2x=0\sin 2x = 0 (not possible)

So, ln⁡(3e2sin⁡x)=+12\ln \left(\dfrac{\sqrt{3}e}{2\sin x}\right) = + \dfrac{1}{2}

⇒3×e2sin⁡x=e12⇒ \dfrac{\sqrt{3} \times \sqrt{e}}{2\sin x} = e\dfrac{1}{2}

⇒sin⁡x=32⇒ \sin x = \dfrac{\sqrt{3}}{2}

⇒ {f}_\max = \left(e\right)\dfrac{3}{8} = \dfrac{{e}^{\dfrac{11}{8}}}{e} ⇒ k = e\dfrac{11}{8}

⇒(ke)8+k8e5+k8=e3+e6+e11⇒ {\left(\dfrac{k}{e}\right)}^{8} + \dfrac{{k}^{8}}{{e}^{5}} + {k}^{8} = {e}^{3} + {e}^{6} + {e}^{11}

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