A Question about a trigonometric identity



On Seg, 2009-11-16 at 10:35 -0800, Martin Mallinson wrote:
> My problem of course, is that I had to guess that the expression was a
> simple phase shift, had I not guessed this, I would never have got
> there...

A picture is worth a thousand words:
 (%i1) R: (3^(3/2)*sin(z)-3*cos(z))/4$
 (%i2) plot2d(R, [z, 0, 3*%pi]);

shows that the function R is a sin function (or a co-sine function
depending on you taste).

Regards,
Jaime