Re: [Axiom-developer] how to expand trig functions ?

[Martin Rubey]

Dear François,

I justed tried out what you wrote:

Francois Maltey writes:
 > expand (sin (x+y)) is right, but 

yes.

 > 1/ I can't get expand (sin (2*x)) 

well, the documentation says that expand deals only with sums...
I guess that you would like to have expand sin(n*x) use the chebyshev
polynomials? I think that this would be reasonable.

 > 2/ The result of expand (sin (x+y+z)) doesn't seem complete. 
 >    axiom only apply twice the expanded sin (a+b) and cos (a+b).
 >    I prefer the maple and mupad method. The formula is completly expanded.

It is complete in my axiom:

(23) -> expand sin (x+y+z)

   (23)
     (- sin(x)sin(y) + cos(x)cos(y))sin(z) + cos(x)cos(z)sin(y)
   + 
     cos(y)cos(z)sin(x)
                                                     Type: Expression Integer
did you expect something else?


 > Am I right when I see it's comming from this src/algebra/manip.spad file ?

yes.

Martin