I am trying to solve this system of differential equations, but it doesn't work. What did I do wrong?
from sympy import Function, dsolve, Eq, Derivative, sin, cos, symbols
from sympy.abc import x
t = symbols('t')
x, y = symbols('x, y', cls=Function)
eq = (Eq(Derivative(x(t), t), -2 * Derivative(y(t), t) - 2 * x(t) - 5 * y(t) + 77),
Eq(Derivative(y(t), t), -x(t) - 4 * y(t) + 61))
dsolve(eq)
Here is the error I got:
AttributeError Traceback (most recent call last)
<ipython-input-32-76dbeaa32a73> in <module>
----> 1 soln = dsolve((eq1, eq2))
2 soln
~\anaconda3\lib\site-packages\sympy\solvers\ode\ode.py in dsolve(eq, func, hint, simplify, ics, xi, eta, x0, n, **kwargs)
573 """
574 if iterable(eq):
--> 575 match = classify_sysode(eq, func)
576 eq = match['eq']
577 order = match['order']
~\anaconda3\lib\site-packages\sympy\solvers\ode\ode.py in classify_sysode(eq, funcs, **kwargs)
1954 if matching_hints['no_of_equation'] == 2:
1955 if order_eq == 1:
-> 1956 type_of_equation = check_linear_2eq_order1(eq, funcs, func_coef)
1957 elif order_eq == 2:
1958 type_of_equation = check_linear_2eq_order2(eq, funcs, func_coef)
~\anaconda3\lib\site-packages\sympy\solvers\ode\ode.py in check_linear_2eq_order1(eq, func, func_coef)
1994
1995 def check_linear_2eq_order1(eq, func, func_coef):
-> 1996 x = func[0].func
1997 y = func[1].func
1998 fc = func_coef
AttributeError: 'list' object has no attribute 'func'
This was a bug in SymPy that has already been fixed. Install SymPy 1.8 (latest release):
In [1]: from sympy import Function, dsolve, Eq, Derivative, sin, cos, symbols
...: from sympy.abc import x
...:
...: t = symbols('t')
...: x, y = symbols('x, y', cls=Function)
...: eq = (Eq(Derivative(x(t), t), -2 * Derivative(y(t), t) - 2 * x(t) - 5 * y(t) + 77),
...: Eq(Derivative(y(t), t), -x(t) - 4 * y(t) + 61))
...: dsolve(eq)
Out[1]:
⎡ -t -3⋅t -t -3⋅t ⎤
⎣x(t) = - 3⋅C₁⋅ℯ - C₂⋅ℯ + 1, y(t) = C₁⋅ℯ + C₂⋅ℯ + 15⎦