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I'm trying to sum over the coefficients of a expansion but the sum gives zero. I use the taylor method to expand a function f:

f=sin(x)
ft=f.taylor(x,0,6)

then I need to use the coefficients in a sum, but if I for example do the following:

sum(x^(i)*ft.coefficient(x,i),i,0,5)

I get zero. Any idea why this is happening?

I'm trying to sum over the coefficients of a an expansion but the sum gives zero. I use the taylor method to expand a function f:

f=sin(x)
ft=f.taylor(x,0,6)

then I need to use the coefficients in a sum, but if I for example do the following:

sum(x^(i)*ft.coefficient(x,i),i,0,5)

I get zero. Any idea why this is happening? happening?