Divide the sides of a quadrilateral into three equal parts. The figure formed by connecting and extending adjacent points on either side of a polygon vertex is a parallelogram known as Wittenbauer's parallelogram.
Wittenbauer's Parallelogram
See also
Quadrilateral, Wittenbauer's TheoremExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Wittenbauer's Parallelogram." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/WittenbauersParallelogram.html