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Mathematics Equation Solving Wolfram Language Numerical Computation

NDSolve documentation example doesn't work on 14.1

Posted 4 months ago

NDSolve does not work with 14.1. Using the examples available in the Help, like: s = NDSolve[{y'[x] == y[x] Cos[x + y[x]], y[0] == 1}, y, {x, 0, 30}] leads to an error message: NDSolve::deqn: Equation or list of equations expected instead of False in the first argument {(y^\[Prime])[x]==Cos[x+y[x]] y[x],False}. Any hint ?

NDSolve does not work with 14.1. Using the examples available in the Help, like:

s = NDSolve[{y'[x] == y[x] Cos[x + y[x]], y[0] == 1}, y, {x, 0, 30}]

leads to an error message:

NDSolve::deqn: Equation or list of equations expected instead of False in the first argument {(y^\[Prime])[x]==Cos[x+y[x]] y[x],False}.

Any hint ?

POSTED BY: Pierre Dehez

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Posted 4 months ago

You are right! I did'nt realize that when opening a new Notebook, variables previously defined were still active. Thanks to both of you!

POSTED BY: Pierre Dehez

Posted 4 months ago

As Ahmed said, you seem to have defined `y[0]`. This is usually done by accident using a single `=` instead of a double `==` in an earlier code. You can restart the kernel or try `y[0] =.` or `Clear[y]`. It's trickier when one makes this mistake on the derivative equation. To clear `y'[x]`, you use `Clear[Derivative]` or `y'[x] =.` (this does not seem necessary in the OP's case, though.)