Prop shaft - 90* out or same as front?

I read somewhere, though can't find where about making sure the rear prop shaft is either in exactly the same phase or 90* out to the front to ensure harmonics aren't set up or something (basically results in a rough ride)

Anyone know which way round it is - i.e. are the yolks meant to be the same or 90* out to each other?

* = degrees

rear the two yoke should be in line fronts 1-2 splines out because of angle ,but as general rule yokes should be in line

Perfect, thanks