Difference between fsolve and nSolve? [CAS]

[parisse]

By default fsolve without guess does the change of variable x=tan(t), then bisection on -1.57..1.57. If the solution is outside this interval it can not be reached, therefore nothing is returned.
nSolve calls Newton with default initial guess to 0, in this case it seems to be convergent.
It is important to understand that one should always give an initial guess or interval to a numeric solver. An algorithm can not always guess for you, the user is in the best position to provide an initial guess (with the help of a plot or because you know the interesting range of values of your parameters).