How Many Triangles Are in a Decagon?

By Staff WriterLast Updated Mar 30, 2020 10:38:03 PM ET
ramsd/CC-BY 2.0

A decagon is a ten-sided, closed-plane figure with eight triangles in it. These eight triangles are formed by joining any vertex of the decagon to any other vertex. Thus, the triangles are formed by drawing the diagonals of the decagon.