Differential Equations Question 20

Question: The solution of $ \frac{dy}{dx}=\frac{e^{x}({{\sin }^{2}}x+\sin 2x)}{y(2\log y+1)} $ is

[AISSE 1990]

Options:

A) $ y^{2}(\log y)-e^{x}{{\sin }^{2}}x+c=0 $

B) $ y^{2}(\log y)-e^{x}{{\cos }^{2}}x+c=0 $

C) $ y^{2}(\log y)+e^{x}{{\cos }^{2}}x+c=0 $

D) None of these

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Answer:

Correct Answer: A

Solution:

$ \frac{dy}{dx}=\frac{e^{x}({{\sin }^{2}}x+\sin 2x)}{y(2\log y+1)} $

Therefore $ \int _{{}}^{{}}{(2y\log y+y)dy=\int _{{}}^{{}}{e^{x}({{\sin }^{2}}x+\sin 2x})dx} $

On integrating by parts, we get $ y^{2}(\log y)=e^{x}{{\sin }^{2}}x+c $ .