Initial value problem using partial fractions

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SUMMARY

The discussion centers on solving the initial value problem defined by the differential equation (t+1) dx/dt = x^2 + 1 with the initial condition x(0) = π/4. The user attempted to separate variables and integrate, arriving at the solution x = tan(ln |t + 1|) + π/4. However, the conversation reveals that the problem does not require partial fractions, as the integral of 1/(x^2 + 1) can be solved directly using arctan or complex logarithms. The conclusion emphasizes that partial fractions are unnecessary for this specific problem.

PREREQUISITES
  • Understanding of first-order differential equations
  • Familiarity with integration techniques, particularly arctan and logarithmic functions
  • Knowledge of complex numbers and their logarithmic properties
  • Basic skills in solving initial value problems
NEXT STEPS
  • Study the method of solving first-order differential equations
  • Learn about the properties and applications of arctan and its derivatives
  • Explore complex logarithms and their relevance in integration
  • Investigate the role of partial fractions in solving rational functions
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Students and professionals in mathematics, particularly those focusing on differential equations, as well as educators seeking to clarify concepts related to integration and initial value problems.

gkchristopher
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(t+1) dx/dt = x^2 + 1 (t > -1), x(0) = pi/4

I have attempted to work this by placing like terms on either side and then integrating.

1/(x^2 + 1) dx = 1/(t + 1) dt

arctan x = ln |t + 1| + C

x = tan (ln |t + 1|) + C

pi/4 = tan(ln |0 + 1|) + C

pi/4 = C

x = tan (ln |t + 1|) + pi/4

Is this even close??
This was supposed to be a partial fractions exercise but I'm not seeing how. Thanks for any help.
 
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No, I don't see any need for partial fractions. For the record, you can integrate 1/(x^2+1) by factoring x^2+1=(x+i)(x-i) and get an expression involving complex logs that is equivalent to arctan. But I don't know why you would want to.
 

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