4
votes
2answers
160 views

Reduce with Integer domain, but receive a rational solution

I want to find the integer values $k$ so that D[f[x], x] has integer solutions. I tried ...
2
votes
1answer
123 views

Numerical errors/inaccuracies in ProductLog

Context In cosmology, a fairly accurate model to describe the gravitational potential, $\psi(r)$ of dark matter halos is given by $\psi( r)=\log(1+r)/r$. ...
4
votes
2answers
168 views

Why the inequality does not take into account the domain?

I have this inequality: Reduce[(4000-1000k)/(k-4) < 0] and the answer is k ∈ Reals I would expect ...
5
votes
1answer
286 views

Issue with NSolve

I defined the following function: sw[ θ_, ϕ_, h_] = 1/2 Sin[2 (ϕ - θ)] + h Sin[ϕ] Based upon whether I use Solve or NSolve, ...
11
votes
1answer
154 views

ToNumberField won't recognize Root as an explicit algebraic number

In Mathematica 9.0.1, it appears that ToNumberField will not always recognize a Root object as an explicit algebraic number. ...
11
votes
1answer
208 views

FindInstance returns Indeterminate in version 9, but not in 8

Here is a trivial system of equations in three unknowns for which FindInstance obtains a solution: ...
16
votes
1answer
620 views

Bug in Solve (Mathematica 9)

Just came across the strangest bug under both Mathematica 9.0.0 and 9.0.1. If one enters: Solve[m == p Sin[x] && -Pi/2 < x < Pi/2, x] ... then ...
3
votes
1answer
1k views

NSolve: Mathematica 9 issue

In Mathematica 8 the following expression evaluates and returns a result in terms of InverseFunction: ...
5
votes
1answer
218 views

Incompleteness of FindInstance

I've been playing around with Resolve and FindInstance. I know that Resolve should always ...