Simplifying Derivative(0,t)?

[gomire...@gmail.com]

How do I get Derivative(0,t) simplified? In my code below, I used subs to substitute 0 for b(t) in a formula,

    a(t)*Derivative(b(t), t) + Derivative(a(t), t)

Then I got

    a(t)*Derivative(0, t) + Derivative(a(t), t)

whereas the answer I want is:
    Derivative(a(t), t)

------------

from sympy import *
from sympy.physics.vector import *
from sympy.physics.mechanics import *

a=dynamicsymbols('a')
a_d=dynamicsymbols('a',1)
b=dynamicsymbols('b')
b_d=dynamicsymbols('b',1)

expr = a*b_d + a_d
print expr

expr2 = expr.subs(b, 0)

print expr2
print simplify(expr2)

------------

Thank you,

Iai

[Aaron Meurer]

Use expr2.doit().

Aaron Meurer

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[gomire...@gmail.com]

Thanks.

Since I was using a matrix, I had to apply doit() to every element, like:

    doit = lambda x: x.doit()

    mat.applyfunc(doit)

However, mat.doit() did not work.

2015年1月29日木曜日 15時00分42秒 UTC+9 Aaron Meurer: