Differential equations MOC

Cauchy-Euler differential equations

A Cauchy-Euler ODE or equidimensional ODE is a linear ODE in which each term has equal dimension of the independent variable.

Second order

In the second-order, they have the standard form

๐‘ฅ2๐‘ฆโ€ณ+๐‘Ž๐‘ฅ๐‘ฆโ€ฒ+๐‘๐‘ฆ=0

Solutions are found by finding the roots of the quadratic

๐‘š2+(๐‘Žโˆ’1)๐‘š+๐‘=0

and then

  1. If ๐‘š1 โ‰ ๐‘š2 in general,
๐‘ฆ=๐ถ1๐‘ฅ๐‘š1+๐ถ2๐‘ฅ๐‘š2
  1. In the case ๐‘š1 =๐‘šโˆ—2 and ๐‘š1,๐‘š2 โˆ‰โ„ this may be rewritten as
๐‘ฆ=๐ถ1๐‘ฅ๐‘Žcosโˆ˜lnโก(๐‘ฅ๐‘)+๐ถ2๐‘ฅ๐‘Žsinโˆ˜lnโก(๐‘ฅ๐‘)
  1. If ๐‘š is a repeated root
๐‘ฆ=๐ถ1๐‘ฅ๐‘š+๐ถ2๐‘ฅ๐‘šlnโก๐‘ฅ

Practice problems


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