Polygons and Angles Lecture Notes

Flashcards covering the definitions, types, and names of polygons, parts of a protractor, types of angles, and metric conversions from the July 14, 2026 lecture.

What are the defining characteristics of a polygon?

A polygon is a multi-sided, closed, 2-dimensional (flat) shape.

What three components make up a polygon?

Sides, vertices, and angles.

What defines a Regular Polygon?

A regular polygon is one where each side and all angles are equal.

What defines an Irregular Polygon?

An irregular polygon has unequal lines (sides) and unequal angles.

In terms of angles, what is the requirement for a Convex polygon?

Each angle must be less than or equal to $180^{\circ}$, and there are no gaps.

What is a Concave polygon?

A polygon where at least one angle is more than $180^{\circ}$, characterized by a cave-like indention.

What is the name of a polygon with 3 sides?

Triangle

What is the name of a polygon with 4 sides?

Quadrilateral

What is the name of a polygon with 5 sides?

Pentagon

What is the name of a polygon with 6 sides?

Hexagon

What is the name of a polygon with 7 sides?

Heptagon

What is the name of a polygon with 8 sides?

Octagon

What is the name of a polygon with 9 sides?

Nonagon

What is the name of a polygon with 10 sides?

Decagon

What are the three main parts of a protractor listed in the notes?

Outer scale, inner scale, and center.

What is the definition of an Acute angle?

An angle that is more than $0^{\circ}$ and less than $90^{\circ}$.

What is the measurement of a Right angle?

Exactly $90^{\circ}$.

What is the definition of an Obtuse angle?

An angle that is more than $90^{\circ}$ and less than $180^{\circ}$.

What is the measurement of a Straight angle?

Exactly $180^{\circ}$.

What is the definition of a Reflex angle?

An angle that is more than $180^{\circ}$ and less than $360^{\circ}$.

What is the measurement of a Full Revolution angle?

Exactly $360^{\circ}$.

What is the conversion relationship between centimeters and millimeters?

$$1\,\text{cm} = 10\,\text{mm}$$