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Let \(y=y(x)\) be the solution of the differential equation \({x}^{4}dy+\left(4{x}^{3}y+2\sin x\right)dx=0\), \(x>0,y\le…

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Let \(y=y(x)\) be the solution of the differential equation \({x}^{4}dy+\left(4{x}^{3}y+2\sin x\right)dx=0\), \(x>0,y\left(\frac{\pi }{2}\right)=0\). Then \({\pi }^{4}y\left(\frac{\pi }{3}\right)\) is equal to:

[JEE Main 2026, 23 Jan (Shift 2)]

a

64

b

92

c

81

d

72

✓ Correct answer: c)

81

Explanation

Given: \(\left(x^4 d y+4 x^3 y d x\right)=-2 \sin x d x\)

\(\Rightarrow \int d\left(x^4 y\right)=\int-2 \sin x d x\)

\(\Rightarrow x^4 y=2 \cos x+c\)

As \(y\left(\frac{\pi}{2}\right)=0\)

So, \(c=0\)

Now, \(\left(\frac{\pi}{3}\right)^4 y\left(\frac{\pi}{3}\right)=2 \cos \frac{\pi}{3}\)

\(\Rightarrow \pi^4 y\left(\frac{\pi}{3}\right)=81\)

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