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JEE MainMathematicsToughDefinite Integration

Let
ddx(f(x))=esinxx,x>0, If ∫14\mspace2mu2esinx2x\frac{d}{dx}(f(x)) = \frac{e^{sinx}}{x},x > 0,\ If\ \int_{1}^{4}\mspace{2mu}\frac{2e^{sinx^{2}}}{x}
dx = f(k) - f(1), then one of the possible value of k is.

Show answer and solution
Given, ddx(f(x))=esinxx,x>0\frac{d}{dx}(f(x)) = \frac{e^{sinx}}{x},x > 0
Now,
I=∫14\mspace2mu2esinx2xdxI = \int_{1}^{4}\mspace{2mu}\frac{2e^{sinx^{2}}}{x}dx
put z = x^2, dz =2 dx

∴\therefore
I=∫14\mspace2mu2xesinx2x2dx=∫116\mspace2muesinzzdzI = \int_{1}^{4}\mspace{2mu}\frac{2xe^{sinx^{2}}}{x^{2}}dx = \int_{1}^{16}\mspace{2mu}\frac{e^{sinz}}{z}dz
=[f(z)]116=f(16)−f(1)= \lbrack f(z)\rbrack_{1}^{16} = f(16) - f(1)
∴\therefore f (K) = f(16)
∴\therefore One possible value of k = 16

Source: Grass-G / M-13 Mathematics Paper 4 Nov.docx

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