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How to recompute symbolic expression

asked 2022-05-18 15:50:54 +0100

ThomasLc gravatar image

I have a symbolic expression with symbolic evaluation.

After I whand to eval the function to it's expression but it doent work :

var("x, omega, t")
u = function('u')(x)

eq = u(x=1) == cos(omega*t)

u(x) = e^(2*t*x)



But now if I create again eq equation, this time it works.

eq2 = u(x=1) == cos(omega*t)


Is-it a function recompute to replace easily function by it value ?

The working solution I found isn't practical :

var("x, omega, t")
uf = function('u')(x)

eq = uf(x=1) == cos(omega*t)

u2(x) = e^(2*t*x)

eq.substitute_function(u, u2).show()

I look on subs() and substitute_function() but their behaviour isn't convenient for this case.

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answered 2022-05-18 23:45:30 +0100

Emmanuel Charpentier gravatar image

Possible workaround :

sage: var("x, omega, t");
sage: u=function("u")
sage: def eq():return u(1)==cos(omega*t)
sage: eq()
u(1) == cos(omega*t)
sage: u(x)=e^(2*t*x)
sage: eq()
e^(2*t) == cos(omega*t)

But I fail to see the point...


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Yes thank you, this is a convenient solution.

ThomasLc gravatar imageThomasLc ( 2022-05-19 17:10:22 +0100 )edit

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Asked: 2022-05-18 15:50:54 +0100

Seen: 94 times

Last updated: May 19 '22