is there any form of pattern matching in sage? that should be the basic tool to do something like you mentioned, is it correct?
Maurizio On 25 Lug, 11:35, Renato <renn...@gmail.com> wrote: > On Sat, 24 Jul 2010 11:03:45 -0700 > > > > Jason Grout <jason-s...@creativetrax.com> wrote: > > On 7/24/10 4:38 AM, Renato wrote: > > > Hi, this seems very basic, but I wasn't able to figure it out. > > > Let's say I have a function: > > > > sage: f(t) > > > -4*(5*sqrt(2)*cos(1/2*sqrt(2)*sqrt(5)) - > > > 2*sqrt(5)*sin(1/2*sqrt(2)*sqrt(5)))*sin(1/2*sqrt(5)*t)/(sqrt(5)*sin(1/2*sqrt(2)*sqrt(5))^2 > > > + sqrt(5)*cos(1/2*sqrt(2)*sqrt(5))^2) + > > > 4*(5*sqrt(2)*sin(1/2*sqrt(2)*sqrt(5)) + > > > 2*sqrt(5)*cos(1/2*sqrt(2)*sqrt(5)))*cos(1/2*sqrt(5)*t)/(sqrt(5)*sin(1/2*sqrt(2)*sqrt(5))^2 > > > + sqrt(5)*cos(1/2*sqrt(2)*sqrt(5))^2) - 8 > > > > how do I tell sage to evaluate numerically everything but sin(), > > > cos() and t? I.e. I know this function is in the form > > > > f(t) = a*sin(b*t) + c*cos(d*t) > > > > can I tell sage to put it in this form, evaluating numerically a,b,c > > > and d? > > > > kind regards > > > renato > > > It looks like there is also a -8 at the end: > > ah yes, you're right. > > > sage: f(t)=-4*(5*sqrt(2)*cos(1/2*sqrt(2)*sqrt(5)) > > -2*sqrt(5)*sin(1/2*sqrt(2)*sqrt(5)))*sin(1/2*sqrt(5)*t)/(sqrt(5)*sin(1/2*sqrt(2)*sqrt(5))^2+ > > sqrt(5)*cos(1/2*sqrt(2)*sqrt(5))^2) > > +4*(5*sqrt(2)*sin(1/2*sqrt(2)*sqrt(5)) > > +2*sqrt(5)*cos(1/2*sqrt(2)*sqrt(5)))*cos(1/2*sqrt(5)*t)/(sqrt(5)*sin(1/2*sqrt(2)*sqrt(5))^2+ > > sqrt(5)*cos(1/2*sqrt(2)*sqrt(5))^2) - 8 > > > sage: f.subs_expr(sqrt(5)==sqrt(5).n(),sqrt(2)==sqrt(2).n()) > > t |--> 8.13039327042996*sin(1.11803398874989*t) + > > 12.5656955743861*cos(1.11803398874989*t) - 8 > > > Basically, I used subs_expr to subsititute in numeric values for the > > square roots. > > thanks :) > > > Question to the community at large: > > > It seems like f.n() should do the above (evaluate what it can > > numerically, leave the variables alone). But this doesn't work: > > yes it would be nice indeed to have a more general way of doing this. > > regards > renato -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
