a nonagon.
A regular octadecagon (an eighteen sided polygon) would have nine diagonals.
Hexagon
A polygon with nine lines of symmetry is a regular nonagon, which is a nine-sided polygon. In a regular nonagon, each vertex can be reflected over a line that passes through the center and a vertex, as well as lines that bisect the angles between the vertices. This symmetry results in a total of nine lines of symmetry.
To calculate the measure of a central angle of a regular nine-sided polygon, divide 360 degrees by the number of sides. In this case, divide 360 by 9. The measure of the central angle of a regular nine-sided polygon is 40 degrees.
7 It is not possible for a regular polygon to have exterior angles of 180 degrees or less in plane geometry
40
It is a nonagon. It need not be a regular nonagon.
A regular nonagram has nine sides. It is a nine-sided polygon, also known as a nonagon. In a regular nonagram, all sides and angles are equal.
Each central angle of a regular 9 sided polygon: 360/9 = 40 degrees
Any regular polygon of n sides, has an order of symmetry of n. Therefore, since a nonagon has nine sides, a nonagon has an order of symmetry of 9.
A regular nonagon, which is a polygon with nine sides, has nine lines of symmetry. Each line of symmetry passes through one vertex and the midpoint of the opposite side, or through the midpoints of two opposite sides. This symmetry reflects the equal length and angles of a regular nonagon.
1260/9 ie 140 degrees assuming polygon is regular. Total is not affected by regularity.