I’m creating a 90x90 tridiagonal matrix using the function below, which I store in the variable `A90`

. When I call `inv(A90)`

, I get a matrix of all NaNs, but if I call `inv(Matrix(A90))`

, the inverse is successfully computed. Is this behavior expected?

```
using LinearAlgebra
function central_difference_discretization(N; dfunc = x -> 12x^2 - 2N^2,
dufunc = x -> N^2 + 4N*x,
dlfunc = x -> N^2 - 4N*x,
bfunc = x -> 114ℯ^-x * (1 + 3x),
b0 = 0, bf = 57/ℯ,
x0 = 0, xf = 1)
h = 1/N
d, du, dl, b = map(dfunc, (x0+h):h:(xf-h)), map(dufunc, (x0+h):h:(xf-2h)),
map(dlfunc, (x0+2h):h:(xf-h)), map(bfunc, (x0+h):h:(xf-h))
b[1] -= dlfunc(x0)*b0 # subtract the boundary term
b[end] -= dufunc(xf)*bf # subtract the boundary term
Tridiagonal(dl, d, du), b
end
A90, b90 = central_difference_discretization(90)
typeof(A90) # Tridiagonal{Float64,Array{Float64,1}}
inv(A90) # Produces a matrix of all NaNs
inv(Matrix(A90)) # Successfully computes the inverse
A80, b80 = central_difference_discretization(80)
inv(A80) # Works fine on Tridiagonals smaller than 82x82
```