In describing an elegant construction of a regular pentagon, i'm struggling to find a nice way of describing the following:
A line segment starting at a point partway up one side of a (in this case, but not necessarily, equilateral) triangle, finishing at a point partway up another side, and parallel to the third side (the base).
In other words this line forms the base of a smaller similar triangle which shares an angle with the main triangle.
Is there a name for such a line?
If it starts halfway, it's called midline, I think... Else, its just a parallel I suppose.