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Need solution for RD Sharma maths Class 12 Chapter 21 Differential Equation Exercise 21.10 Question 38 textbook solution.

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Answer : y=\frac{x^{2}}{4}+\frac{c}{x^{2}}

Give : \tan x \frac{d y}{d x}+2 y=x^{2}

Hint : Using \int \frac{1}{x} d x \text { and } e^{\log e^{x}}=x

Explanation : \tan x \frac{d y}{d x}+2 y=x^{2}

Divide by x

   \begin{aligned} &=\frac{d y}{d x}+\frac{2 y}{x}=x \\ &=\frac{d y}{d x}+\left(\frac{2}{x}\right) y=x \end{aligned}

This is a linear differential equation of the form

      \begin{aligned} &\frac{d x}{d y}+P y=Q \\ &P=\frac{2}{x} \text { and } Q=x \end{aligned}

The integrating factor If of this differential equation is

       \begin{aligned} &I f=e^{\int P d x} \\ &=e^{\int \frac{2}{x} d x} \\ &=e^{2 \int \frac{1}{x} d x} \\ &=e^{2 \log x} \; \; \; \; \; \; \; \; \; \; \; \; \quad\left[\int \frac{1}{x} d x=\log x+C\right] \end{aligned}

        \begin{array}{ll} = & e^{\log x^{2}} \\ =x^{2} & {\left[e^{\log e^{x}}=x\right]} \end{array}

Hence, the solution is

         \begin{aligned} &y I f=\int Q I f d x+C \\ &=y x^{2}=\int x x^{2} d x+C \\ &=y x^{2}=\int x^{3} d x+C \\ &=y x^{2}=\frac{x^{4}}{4}+C \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \quad\left[\int x^{n} d x=\frac{x^{n+1}}{n+1}+C\right] \end{aligned}

Divide by x^{2}

         =y=\frac{x^{2}}{4}+\frac{c}{x^{2}}

      

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