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Best answer by AlanStevens

Val sends his thanks to all, and notes that he has solved the problem using Mathematica:

асф линза1.jpgкод Вольфрам.jpg

2 replies

23-Emerald IV
April 16, 2025

Hi Valery,

The highest derivative of the sought function must be on the LHS of the equation.
Reason: Odesolve uses the/an RK4 algorithm, where the (highest derivative of the) sought function must be expressed as an explicit definition.

 

Success!
Luc

25-Diamond I
April 16, 2025

According to the help "The ODE must be linear in their highest derivative term" which is not the case when the derivative is used as argument of arctan.

AlanStevens19-TanzaniteAuthorAnswer
19-Tanzanite
April 18, 2025

Val sends his thanks to all, and notes that he has solved the problem using Mathematica:

асф линза1.jpgкод Вольфрам.jpg