[scheduled:: 2025-01-09]

Introduction to Polygons

Links and useful resources

• gr10's Geometry >>>START HERE<<<
• AoPS Alcumus
• Handwritten math converter
• Big Ideas Geometry textbook
• GeoGebra Online Geometry Constuction Tool
• Two-column math templates
• Proofs unit slides from mathgiraffe.com
• Proofs unit printables for two-column proofs

Concept summary and connections

• polygon names
• convex polygon
• regular polygon
• interior angles
• exterior angles
• triangle method for interior angles

Worked examples

Show how to find the sum of exterior angles for any n-gon

Formulas

• The sum of interior angles for any n-gon (even non-convex) is $\frac{180(n-2)}{n}\mathrm{°}$
• The sum of EXTERIOR angles for any CONVEX polygon is $360\mathrm{°}$

Media resources

• Youtube search for "polygon names"
• Youtube search for "regular polygon"
• Youtube search for "interior angles"
• Youtube search for "exterior angles"
• Youtube search for "triangle method for interior angles"

Guided practice

• Find the number of sides in a regular polygon whose interior angles measure $172\mathrm{°}$
• ABCDEFGHIJKLMNO is a regular 15-gon. Find $\mathrm{\angle }ACB$, $\mathrm{\angle }ACD$, and $\mathrm{\angle }ADE$

Homework

• #hw (geometry) 9.2 Angles in a Polygon (p. 246) 2025-01-13