Polygon Definitions+ - 9th Geometry

Defining types of polygons, and stuff like central angles and radius

What is a regular polygon?

A polygon where all sides and interior angles are congruent. A regular polygon is equiangular and equilateral

What does “equiangular” mean?

Congruent angles

What does “equilateral” mean?

Congruent sides

What is an irregular polygon?

All sides and interior angles do not have the same measure.

What is a convex polygon?

All interior angles are less than 180 degrees

What is a concave polygon?

One or more of the interior angles is greater than 180 degrees (hint to identify them: point into the polygon)

What is a vertex?

A point where 2+ line segments or rays meet

What is a diagonal?

Segment of a polygon that connects 2 non-consecutive vertices

What is the interior angle sum of a triangle?

180 degrees

What is the formula to find the interior angle sum of a polygon?

(n-2)x180 [where “n” = the number of sides]

Sum of exterior angles for any polygon?

360 degrees

What is a central angle?

angle whose vertex is the center of the polygon. Rays or sides of the angle have their endpoints at the side of the regular polygon

What is a radius, regarding regular polygons?

A line segment that connects the center of the polygon [central angle vertex] and a vertex [that’s not the central angle. So, a vertex where two of the sides of the polygon meet]

What is an apothem?

A line segment that connects the center of the polygon [central angle vertex] to the midpoint of a side of the polygon

What is a perimeter?

The total length around the outside of a two-dimensional shape

What is sin in relation to polygons?

opposite/hypotnuse [1/2 the side/radius]

What is cos in relation to polygons?

adjacent/hypotnuse [apothem/radius]

What is tan in relation to polygons?

opposite/adjacent [1/2 of a side/apothem]