This note shows the trigonomic functions employed in rotation matrices for a typical graphics system. It shows the trigonomic functions where you normally see the trigonomic values -1 to +1. You'll see how those functions multiply together when rotation matrices, that can rotate vetors about single axes, are multiplied together to form rotation matrices that can rotate vectors about multiple axes.
See NOTES15# for an illustration of matrix multiplication.
The order that you multiply rotation matrices together is usually critical to a game (as is the order that you apply matrices to vectors to rotate them) for the following reason:-
The resulting multipled matrix actually "remembers" the order of the multiplication of the single axis roation matrices... so if you apply it to a vector to rotate it then it's exactly like you had applied the single axis rotation matrices to the vector one after another in the order they were multiplied. So the main advantage to multiplying rotation matrices together is so that you can rotate a vector about upto 3 axes in one go (saving processing time if you keep reusing that matrix).