(This item pertains to the check boxes on the General tab of the Setup Options dialog box. You can open it through the F5 key or through the Edit | Preferences | Setup menu option.)
With this option selected, polar angles will follow standard DMIS Polar Convention.
XY Plane (PLUS Z or MINUS Z) coordinate 'a' is the angle from the x-axis towards the y-axis.
YZ Plane (PLUS X or MINUS X) coordinate 'a' is the angle from the y-axis towards the z-axis.
ZX Plane (PLUS Y or MINUS Y) coordinate 'a' is the angle from the z-axis towards the x-axis.