subs command does not create symbolic variable?

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nafis irtija
nafis irtija el 19 de Jun. de 2015
Comentada: John D'Errico el 19 de Jun. de 2015
I am using MATLAB R2011a. I have symbolic math toolbox installed. When I use the "subs" command to replace a value in a symbolic variable, instead of symbolic variable a normal variable is created ... My code is
>> f=int(g,x)
f =
asin((2*x)/5 - 4/5)/2
>> subs (f,x,3)
ans =
0.2058
What am missing?
  2 comentarios
nafis irtija
nafis irtija el 19 de Jun. de 2015
In the mathworks tutorial video they wrote
>>f3=subs(f,x,3)
and the variable f3 was symbolic.when i write the same code,f3 is not symbolic.and they used "eval(f3)" to get the value 0.2058.when I write
eval(f3)
it gives an error.
John D'Errico
John D'Errico el 19 de Jun. de 2015
It is difficult to know, since your version is so old. It works fine for me. For eample, since I do not have g, I did this:
syms x
f = asin((2*x)/5 - 4/5)/2
f =
asin((2*x)/5 - 4/5)/2
subs(f,x,3)
ans =
asin(2/5)/2
with no problems. But I am using the current release.

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Respuestas (1)

Martin Brown
Martin Brown el 19 de Jun. de 2015
You've evaluated
asin((2*3)/5 - 4/5)/2
which is indeed 0.2058. It's no longer symbolic?

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