Sympy – limit() error : Result depends on the sign… here is a solution to the problem.
Sympy – limit() error : Result depends on the sign
I’m trying to solve the following problem:
Applying the following I got the correct answer.
α, t, x = symbols('α t x')
integrate(α*x*exp(-α*x), (x, 0, oo), conds='none')
To check the solution (1/α), I tried the following.
limit(integrate(α*x*exp(-α*x), (x, 0, t), conds='none'), t, oo)
But this produces a NotImplementedError
: Result depends on the sign of -sign(α) and a further **NotImplementedError** that is not described. The function works for real numbers, but not for oo. How do I fix this?
Solution
Adding the parameter positive = true to the symbols function alleviates this problem.
α, t, x = symbols('α t x', positive = True)
func = integrate(α*x*exp(-α*x), (x, 0, t), conds='none')
(limit(func, t, oo))
Yield 1/α