~~maxima expression~~Sage and Maxima expression not compatible

Hi,

I got another problem relating to this question http://ask.sagemath.org/question/8137/unable-to-make-sense-of-maxima-expression/ and many other of that kind (sorry for opening another question). If I use

```
sum(-1**(i+1)/(2*i-1)**3*(sin(pi*(2*i-1)/2*(r1+r2))*sin(pi*(2*i-1)/2*(r1-r2))),i,1,oo)
```

in the shell, I get

```
TypeError: unable to make sense of Maxima expression 'imagpart(f[4,3]([1/2,1/2,1/2,1],[3/2,3/2,3/2],e^-(2*I*pi*r1)))' in Sage
```

I read in http://trac.sagemath.org/ticket/9825 that the problem concerns the temporary variables. But is there a possibility to reformulate the problem to get to the solution? Btw, I'm using Sage v6.2 on a LinuxMint machine.