Lung cancer is the top cause of cancer deaths in both men and women. But this wasn't always the case. Prior to the widespread use of mechanical cigarette rollers, lung cancer was rare. Today, smoking causes nearly 9 out of 10 lung cancer deaths, while radon gas, pollution, and other things play a smaller role.
From Wikipedia, the free encyclopedia. A plane symmetry is a symmetry of a pattern in the Euclidean plane: that is, a transformation of the plane that carries any directioned lines to lines and preserves many different distances. If one has a pattern in the plane, the set of plane symmetries that preserve the pattern forms a group. The groups that arise in this way are plane symmetry groups and are of considerable mathematical interest. A symmetry plane is a three-dimensional object's symmetry axe. There are several kinds of plane symmetry groups: Reflection groups.
When the folded part sits perfectly on top (all edges matching), then the fold line is a Line of Symmetry. Here I have folded a rectangle one way, and it didn't work. So this is not a Line of Symmetry. But when I try it this way, it does work (the folded part sits perfectly on top, all edges matching): So this is a Line of Symmetry.