[[File:varignon_parallelogram.svg|thumb|[[Proof without words]] of Varignon's theorem: {{olist
<br/>1. |An arbitrary quadrilateral and its diagonals.
<br/>2. |Bases of similar triangles are parallel to the blue diagonal.
<br/>3. |Ditto for the red diagonal.
<br/>4. |The base pairs form a parallelogram with half the area of the quadrilateral, ''A<sub>q</sub>'', as the sum of the areas of the four large triangles, ''A<sub>l</sub>'' is 2 ''A<sub>q</sub>'' (each of the two pairs reconstructs the quadrilateral) while that of the small triangles, ''A<sub>s</sub>'' is a quarter of ''A<sub>l</sub>'' (half linear dimensions yields quarter area), and the area of the parallelogram is ''A<sub>q</sub>'' minus ''A<sub>s</sub>''.]]