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The solution of the equation (dy)/(dx)=...

The solution of the equation `(dy)/(dx)=(x(2logx+1))/(sin y+y cos y)` is

A

`y sin y=x^(2)log x +(x^(2))/(2) +c `

B

`y cos y =x^(2)(log +1)+c`

C

`y cos y= x^(2)log x +(x^(2))/(2) +c`

D

`y sin y =x^(2)log x +c`

Text Solution

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The correct Answer is:
To solve the differential equation \(\frac{dy}{dx} = \frac{x(2\log x + 1)}{\sin y + y \cos y}\), we will use the method of separation of variables. Here are the steps to solve the equation: ### Step 1: Separate the Variables We can rearrange the equation to separate the variables \(y\) and \(x\): \[ (\sin y + y \cos y) dy = x(2 \log x + 1) dx \] ### Step 2: Integrate Both Sides Now, we will integrate both sides: \[ \int (\sin y + y \cos y) dy = \int x(2 \log x + 1) dx \] ### Step 3: Solve the Left Side Integral For the left side, we can break it down: 1. \(\int \sin y \, dy = -\cos y\) 2. For \(\int y \cos y \, dy\), we will use integration by parts: - Let \(u = y\) and \(dv = \cos y \, dy\). - Then \(du = dy\) and \(v = \sin y\). - Using integration by parts: \(\int u \, dv = uv - \int v \, du\): \[ \int y \cos y \, dy = y \sin y - \int \sin y \, dy = y \sin y + \cos y \] Combining these results, we have: \[ \int (\sin y + y \cos y) dy = -\cos y + (y \sin y + \cos y) = y \sin y \] ### Step 4: Solve the Right Side Integral Now, we will solve the right side integral: \[ \int x(2 \log x + 1) dx \] We can split this into two parts: 1. \(\int x \cdot 2 \log x \, dx\) and 2. \(\int x \, dx\). For \(\int x \cdot 2 \log x \, dx\), we will again use integration by parts: - Let \(u = \log x\) and \(dv = 2x \, dx\). - Then \(du = \frac{1}{x} \, dx\) and \(v = x^2\). Using integration by parts: \[ \int 2x \log x \, dx = 2 \left( x^2 \log x - \int x^2 \cdot \frac{1}{x} \, dx \right) = 2 \left( x^2 \log x - \frac{x^3}{3} \right) \] Now, for the second part: \[ \int x \, dx = \frac{x^2}{2} \] Combining these results, we have: \[ \int x(2 \log x + 1) \, dx = 2 \left( x^2 \log x - \frac{x^3}{3} \right) + \frac{x^2}{2} \] ### Step 5: Combine Results Now we combine both sides: \[ y \sin y = 2 \left( x^2 \log x - \frac{x^3}{3} \right) + \frac{x^2}{2} + C \] ### Final Result Thus, the solution of the differential equation is: \[ y \sin y = 2x^2 \log x - \frac{2x^3}{3} + \frac{x^2}{2} + C \]
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