try expand(trigsimp(trigexpand( sqrt(b^2+a^2)*sin(x+atan(b/a)) ))); but that is in the reverse direction. Your notion of simplification is more like complification. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.math.utexas.edu/pipermail/maxima/attachments/20080905/6f6eedf1/attachment.htm