Right Angles, Acute Angles, and Obtuse Angles

- Right angles measure 90 degrees

- Acute angles measure less than 90 degrees

- Obtuse angles measure more than 90 degrees

Polygons

In geometry, a polygon is a plane figure that is described by a finite number of straight-line segments connected to form a solid plane region.

Names of Polygons

• A 3-sided polygon is called a TRIANGLE

• A 4-sided polygon is called a QUADRILATERAL

• A 5-sided polygon is called a PENTAGON

• A 6-sided polygon is called a HEXAGON

• A 8-sided polygon is called a OCTAGON

• A 9-sided polygon is called a NONAGON

• A 10-sided polygon is called a DECAGON

Find the Measure of One Interior Angle

Interior angles of regular polygons

Find the sum of interior angles using the formula 180n-360 as before. Then divide by the number of sides to find the value of one angle.