# Polygons Geometry Unit 2.

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Polygons Geometry Unit 2

Polygon: Origin: Greek “Poly-” meaning “many” and “-gon” meaning “angle” Definition: a 2-dimensional, closed, shape made of three or more straight lines.

NOT A POLYGON! POLYGON! POLYGON! NOT A POLYGON! POLYGON! POLYGON!

The BASIC Polygons – Part 1
# of Sides Name Picture Sum of Interior 3 4 5 6 Triangle Quadrilateral Pentagon Hexagon

The BASIC Polygons – Part 2
# of Sides Name Picture Sum of Interior 7 8 9 10 Heptagon Octagon Nonagon Decagon

The BASIC Polygons – Part 3
# of Sides Name Picture Sum of Interior 12 n dodecagon n-gon

Sum = 180(n-2) n = the number of sides Sum of the interior
We can find the sum of the interior angles of any polygon using the formula Sum = 180(n-2) n = the number of sides Back to the chart

The BASIC Polygons – Part 1
# of Sides Name Picture Sum of Interior 3 4 5 6 Triangle 180° Quadrilateral 360° Pentagon 540° Hexagon 720°

The BASIC Polygons – Part 2
# of Sides Name Picture Sum of Interior 7 8 9 10 Heptagon 900° Octagon 1080° Nonagon 1260° Decagon 1440°

The BASIC Polygons – Part 3
# of Sides Name Picture Sum of Interior 12 n dodecagon 1800° n-gon 180(n-2)°

The algebra of Sum of the interior
Find the value of x. (4x) (2x + 9) + (3x + 8) = 540 113° X = 33

More Interior Angle Stuff
The sum of the interior angles of a polygon is degrees. What is the name of the polygon? 11-gon We’ll know tomorrow

Sum of the Exterior The sum of the exterior angles of a polygon is simple … it always equals 360°

A single exterior angle
Find the measure of an exterior angle of a regular heptagon. Round to the nearest tenth if necessary. 51.4°

They are supplementary
Interior and Exterior What is the relationship between an individual interior and exterior angle? They are supplementary

More Algebra Find the value of x. x x = 540 138° 100° X = 64