In a sketch, when dimensioning from a solid line to a construction line, if the two are parallel, one can either dimension the distance, or double the distance (simply by pulling the smart dim across the construction line), a great feature that's been with us forever that I use about 20 times a day.  It is especially useful for diameter work when making the beginnings of a revolve.

Is it possible to do this with angles also?  When I have a solid line intersecting a construction line (that will become a mirror line), I always have to dimension what will ultimately become half of the angle.

Thanks.