Dropping higher order terms in polynomials.
could you please let me know how to write a code? I just get started with the SAGE and met a trouble. When I put the followings
then the output is a polynomial function with 16th order. But I wanted to drop the higher order terms and just take 3 tems. However I have no idea how to do it. It seems the truncate() or power_series(ZZ) don't work for the exponential function. Could anyone give me the solution?