1. **State the problem:** We need to solve the differential equation $$y' = (1 + y^2) + \sin x$$ where $y'$ denotes the derivative of $y$ with respect to $x$.
2. **Rewrite the equation:** The equation is $$\frac{dy}{dx} = 1 + y^2 + \sin x$$.
3. **Check if separable:** The right side is $1 + y^2 + \sin x$, which is not separable into a product of a function of $x$ and a function of $y$.
4. **Try substitution or rearrangement:** This is a nonlinear first-order ODE. Notice that $y' - y^2 = 1 + \sin x$.
5. **Recognize the Riccati form:** The equation is of the form $$y' = y^2 + f(x)$$ with $f(x) = 1 + \sin x$.
6. **Solve Riccati equation:** Riccati equations can be transformed if a particular solution is known or by substitution $y = -\frac{u'}{u}$.
7. **Use substitution:** Let $$y = -\frac{u'}{u}$$ then $$y' = -\frac{u''u - u'^2}{u^2}$$.
8. **Substitute into original equation:**
$$-\frac{u''u - u'^2}{u^2} = 1 + \sin x + y^2 = 1 + \sin x + \left(-\frac{u'}{u}\right)^2 = 1 + \sin x + \frac{u'^2}{u^2}$$
9. **Multiply both sides by $u^2$:**
$$- (u''u - u'^2) = (1 + \sin x) u^2 + u'^2$$
10. **Simplify:**
$$-u''u + u'^2 = (1 + \sin x) u^2 + u'^2$$
11. **Cancel $u'^2$ on both sides:**
$$-u''u = (1 + \sin x) u^2$$
12. **Divide both sides by $u$ (assuming $u \neq 0$):**
$$-u'' = (1 + \sin x) u$$
13. **Rewrite:**
$$u'' + (1 + \sin x) u = 0$$
14. **Interpretation:** This is a second-order linear differential equation for $u(x)$.
15. **Summary:** To solve the original nonlinear ODE, solve the linear ODE $$u'' + (1 + \sin x) u = 0$$ and then find $$y = -\frac{u'}{u}$$.
16. **Final answer:** The general solution to the original equation is $$y = -\frac{u'}{u}$$ where $u$ satisfies $$u'' + (1 + \sin x) u = 0$$.
This second-order ODE may require numerical or special function methods to solve explicitly.
Riccati Equation 83C0C4
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