Solve Riccati Equation: dy/dx + y2 = 1 + x2

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SUMMARY

The discussion focuses on solving the Riccati equation dy/dx + y² = 1 + x², with y(x) = x as a particular solution. The equation is rearranged into Riccati form and transformed using the substitution v = 1/(y - y(x)), leading to a separable linear equation. The integrating factor μ is determined to be e^(-x²), allowing the equation to be integrated and expressed in terms of the error function. The final solution is y = x + (2e^(-x²))/(√π erf(x) + d).

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  • Understanding of Riccati equations
  • Familiarity with differential equations and integrating factors
  • Knowledge of the error function and its properties
  • Basic calculus skills, including integration techniques
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  • Study the properties and applications of Riccati equations
  • Learn about integrating factors in first-order differential equations
  • Explore the error function and its significance in mathematical analysis
  • Practice solving differential equations using substitution methods
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Students and mathematicians interested in differential equations, particularly those studying Riccati equations and their solutions. This discussion is beneficial for anyone looking to deepen their understanding of integrating factors and the error function in mathematical contexts.

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Homework Statement



So I came across one of these equations. Solve : dy/dx + y2 = 1 + x2 when y(x) = x is a particular solution.

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The Attempt at a Solution



So I re-arranged my equation into Riccati form : dy/dx = 1 + x2 - y2

Now I let : v = [itex]\frac{1}{y-y(x)}[/itex] so that y = x + 1/v

Thus : dy/dx = -(1/v2)dv/dx + 1

Subbing these back into my equation yields :

(-1/v2)dv/dx + 1 = 1 + x2 - (1/v + x)2

Simplifying everything, I get a seperable linear equation in standard form :

dv/dx - 2xv = 1 (***)

So my integrating factor μ must satisfy :

dμ/dx = -2xμ which implies that μ = e-x2

So now my equation (***) can be re-written as :

d/dx [e-x2v] = e-x2

Integrating both sides and then expressing my integrand in terms of the error function gives me the final answer :

v = [itex]\frac{\sqrt{\pi} \space erf(x) + d}{2e^{-x^2}}[/itex]

And finally plugging v back into y yields my solution :

y = [itex]x + \frac{2e^{-x^2}}{\sqrt{\pi} \space erf(x) + d}[/itex]

Is this correct? This is my first try at one of these so I'm still in the not sure what I'm doing moment.
 
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