Please Help!

PLease help me!

I write a program for "Series" of Fourier but i have 2 problems:

First, i obtain the correct coeficients but lua write without format (for example : 2xsin(2x.....)/(n^2))
Can i obtain with the same format of the "Principal" (in principal menu) because is more "comprensive" and clarity.

The code is like this... the problem is for my use of sintaxis?
bn=cas.tofrac((2/T)*((cas.integ(function*cas.sin("n"*frec*"t"),"t",a1,b1))))

Second, How can i plot the function total? The command showgraph not works?

PLease help me and thanks a lot!!!
PD: Sorry for my english , im spanish