This is the node set up I used.  I used the Tile 012 texture from AmbeintCG.com for the floor.

It seems to me that 360° of rotation of the Z value equals 2π (6.283185), thus 180° of equals π (3.14159) and so 90° of rotation equals ½π (1.570796). If so, then all other measures of rotation would therefore be in accordance. Any one feel free to let me know if I have this wrong.