> I only need to displace it among the the existing three axes. That is exactly what these three matrices do. R_x depends on a single parameter and tells you h

> I only need to displace it among the the existing three axes. That is exactly what these three matrices do. R_x depends on a single parameter and tells you how much you rotate around the x-axis. R_y tells you how much you rotate around the y-axis and R_z for the z-axis. Any rotation can be written as a product of these three (which then is a single 3x3 matrix depending on three parameters).