7
Seven
A 7 sided heptagon contains 5 triangles.
A heptagon is a polygon with 7 sides.
A heptagon has seven sides.
In a regular heptagon, there are 7 lines of symmetry because there is one line of symmetry for every side.
A heptagon has seven sides, so a regular heptagon has seven lines of symmetry (they run from each vertex to the middle of the opposite side).
7, 9 and 10 respectively
One more side
A heptagon
That's a Heptagon or a septagon
It has 1 more side
7 times the length of a side, if it's a regular heptagon.