Oops, case 4 ended at the end of the message...
On 2 fév, 15:06, Nicolas <nicolas.fresseng...@gmail.com> wrote:
> Here is some to-my-opinion strange behaviour of trig_expand :
>
> #Declare real variables
> var('a b c')
> assume([a,'real'],[b,'real'],[c,'real'])
> assumptions()
> ---> [a is real, b is real, c is real]
>
> #Case 1
> sin(a+b).trig_expand()
> ---> sin(a)*cos(b) + sin(b)*cos(a)
>
> #Case 2
> sin((a+b)/2).trig_expand()
> ---> sin(1/2*a)*cos(1/2*b) + sin(1/2*b)*cos(1/2*a)
>
> #Case 3
> sin((a+b)/c).trig_expand()
> ---> sin((a + b)/c)
>
> #Case 4
> sin((a/c+b/c)).trig_expand()
>
> ________
> In case 3, the expansion is not done. I wonder if it would be possible
> to do it. Obviously, if the sine argument was rational expanded before
> trig expansion, it would work but none seem to work on the whole
> expression.
>
> Any idea ?
>
> PS: I am actually using this in an expression where doing this
> expansion would simplify a lot and I would have expected simplify_full
> to see it... which it does not, I suspect because of this.
> ---> sin(a/c)*cos(b/c) + sin(b/c)*cos(a/c)
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