1. Classifying Polygons

2. What is a polygon?
Definition: Closed plane figure with at least three sides
Sides only meet at their endpoints (called vertices)
Regular polygons have all sides and angles congruent

3. Classifying Polygons TRIANGLE 3 180° 60° QUADRILATERAL 4 2 360° 90°
NAME
# OF SIDES
# OF DIAGONALS
SUM OF INTERIOR ANGLES
EACH ANGLE
TRIANGLE 3
180°
60°
QUADRILATERAL 4 2
360°
90°
PENTAGON 5
540°
108°
HEXAGON 6 9
720°
120°
SEPTAGON/ HEPTAGON 7
OCTAGON 8
NONAGON
DECAGON 10

4. What is the rule for regular polygons?
Any polygon with sides n:
Sum of interior angles formula:(n-2) × 180°
Each angle formula: (n-2) × 180° / n

5. How are triangles classified?
Acute- three acute angles (less than 90°)
Right- one right angle
Obtuse- one obtuse angle (more than 90°)
Equilateral- three congruent sides
Isosceles- two congruent sides
Scalene- no congruent sides

6. How are quadrilaterals classified?
Trapezoid- one pair of parallel sides
Parallelogram- both pairs of opposite sides are parallel
Rhombus- four congruent sides
Rectangle- four right angles
Square- four right angles and four congruent sides