Question: Functions as matrix elements???? I want to see the algebraic expressions behind the matrix elements, but also do calculations

Hi,

I am an absolute beginner with Maple and am appreciating any help.

Basically, I want to use maple because it can deal with algebraic expressions. For example with Matrixmultiplication I don't just want to see the final result, but also I want to see the algebra behind each matrix element. 

So I have defined the following 2 matrices :

rot_x := matrix([[1,0,0], [0, cos(alpha), -sin(alpha)], [sin(alpha), cos(alpha), 0]]); 

rot_y := matrix([[cos(alpha), 0, sin(alpha)],[0,1,0],[-sin(alpha), 0, cos(alpha)]]);

When I now multiply Rot_x with Rot_Y, Maple gives me a nice output of the algebraic expression behind each matrix element...which is great...

Result :=multiply(Rot_x, Rot_y);   ====> shows a lot of cos(alpha)* sin(alpha) etc....

...But now, I would like to assign a value to the variable alpha (e.g. 90degrees), so that the matrices rot_x, rot_y and result appear just with the numbers in it, instead of algebraic expressions......

It would be great if somebody gave me a quick kickstart......

THANKS for any contribution.....