In fu.py there are several functions to manipulate trigonometric expressions; in your example you can use TR8 to expand products of sin-cos to sums;
``` from sympy.simplify.fu import TR8 from sympy.simplify.simplify import _mexpand P = (D + F*sin(x) + G*cos(x) + H*sin(2*x) + J*cos(2*x))**2 r = _mexpand(TR8(_mexpand(P))) ``` what is missing is the collection of the coefficients; it is easy to write a function collecting terms, but I suspect that there is already a simple way in SymPy to do this. On Friday, February 7, 2014 8:28:20 AM UTC+1, Alex Clifton wrote: > > I was wondering if there was a way to “guide” sympy in performing trig > identities to get the output into a specific form? Below, I go into detail > and have attached a working version of the file for reference. > > In the expression of P, the coefficients D, F, G, H, and J are assumed to > be real valued. I have left some commented print statements to show the > different simplify options I have tried. I have performed this calculation > by hand and I know there are several trig substitutions that need to be > made in order to get the final expression in the form that I would like. > That form is to get rid of all powers of trig functions greater than 1 by > appropriate substitutions. Of course, I cannot expect sympy to know that I > want things in this form so I am not surprised when the different simplify > statements do not give me that form. I was wondering what would be the > best way to guide sympy in order to get the final output of P to be in the > following form: > > K + Lsin(x) + Mcos(x) + Nsin(2x) + Qcos(2x) + Rsin(3x) + Scos(3x) + > Tsin(4x) + Vcos(4x) > > Where K, L, M, N, Q, R, S, T, and V are now combinations of the original > D, F, G, H, and J. > > By the way, I am not as concerned now about the coefficients as I am > getting rid of the higher powers of the trig functions. Although if people > would like to weigh in on that, that would be great. If more detail is > needed, please let me know and I’d be happy to provide it. > > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.
