I guess you mean in the sketcher - before you revolve/extrude.
While in sketcher find the name of the driving angle (for example sd35) edit the value of the driven angle to by writing the name of the driving angle and accept to add the relation.
In sketcher go to TOOLS>RELATIONS and type "angle1=angle2" Substitute the "angle1" and "angle2" for the angle dimensions name. Make sure you got both angle dimensions on the sketch, so you know there name. For example: sd3=sd5 and hit ok. Now the angles will be equal.