Hi,

I have found that the only difference between when I select "line" or "centerline" in whether the option "For construction" is checked. I searched and read Construction Geometry in SW online help and found that the description seems to suggest that they are basically just "auxiliary line" used in geometry proofs, which are visual aids to drawing and thinking, but not part of the original figure, and are always drawn in dashed lines. They are the same thing, aren't they?

Qi