D[R*Cos[w*t], {t,2}]

[sn6uv]

Terms coming from the sympy conversion are apearing in the following expression

>> D[R*Cos[w*t], {t,2}]
 =  -R w ^ 2 Cos[t$1 w]

expected:

-(R*w^2*Cos[t*w])

Reported here.

[GitAnt]

This problem traces back to the rule found at the lines 119-120 in mathics/builtin/calculus.py. In general it comes from a name clash between a dummy variable in a module and an argument of the same module. For example, it can be reproduced by defining:

deri[expr_,x_,n_]:=Module[{t}, Nest[Function[{tmp}, D[tmp, x]], expr, n]]

and then trying to calculate

deri[Cos[t],t,1]

while

deri[Cos[a],a,1]

works just fine. Any idea on how to fix this?

[bnjones]

It looks like this is fixed now that #202 has been merged. Thanks @GitAnt!