How to simplifiy a*sin(x)+b*cos(x)



On Fri, Sep 5, 2008 at 12:14 PM, Richard Fateman <fateman at cs.berkeley.edu>wrote:

>  try expand(trigsimp(trigexpand(    sqrt(b^2+a^2)*sin(x+atan(b/a))  )));
>
but that is in the reverse direction.
>

This proves the equality, but as you say doesn't perform the transformation
the user wants to perform.


> Your notion of simplification is more like complification.
>

No, it is more like "transformation" to another form.  And a useful
transformation.  I can't think of a straightforward way to perform this
transformation in general in Maxima; I don't think the pattern matcher is
powerful enough to find the appropriate subexpression of, e.g.

         a*sin(q)+b*cos(r)+c*cos(q)

without explicitly being told it is looking for terms in sin/cos(q).

             -s