On 28/03/2021 19:48, 'Aditya Saxena 4-Year B.Tech. Electronics
Engineering' via sympy wrote:
Hi developers,
I am Aditya Saxena, a 2nd year ECE student at IIT BHU. I wish to
contribute to the SymPy community but I am new to SymPy and so to get
a better understanding of it, I was going through the tutorial as
suggested in the documentation. While going through it I noticed that
the Integration function is not giving out the 'constant term' in the
output expression.
For example in the following code:
>>> from sympy import *
>>> x = symbols('x')
>>> a = Integral(cos(x)*exp(x), x)
>>> Eq(a, a.doit())
we get the output as:
Eq(Integral(exp(x)*cos(x), x), exp(x)*sin(x)/2 + exp(x)*cos(x)/2)
I am certainly not a developer here - though I would love to reach the
level of understanding of SymPy that would make that possible!
I looked in the online documentation (just using GOOGLE) and found this:
Note that SymPy does not include the constant of integration. If you
want it, you can add one yourself, or rephrase your problem as a
differential equation and use |dsolve| to solve it, which does add the
constant (see Solving Differential Equations
<https://docs.sympy.org/latest/tutorial/solvers.html#tutorial-dsolve>).
I think the real problem is that to add a constant of integration, SymPy
would have to choose a symbol to represent it, and that might already be
in use. I guess if you write an indefinite integral, you are supposed to
know how to use it. You can also get round the problem using a dummy
limit, for example:
Integral(cos(x)*exp(x), (x,0,c))
I wondered why you wrote your example in a convoluted way - using
Integral (which needs subsequent activation with doit) as opposed to
integrate, which doesn't, and why you needed to use Eq. To obtain an
integral simply write:
integrate(cos(x)*exp(x), x)
David
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