Angles, Triangles & Polygons

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Names of Angles

Acute Angle

$\theta < 90°$

Right Angle

$\theta = 90°$

Obtuse Angle

$90° < \theta < 180°$

Reflex Angle

$\theta > 180°$

Angle Properties

$\angle$ on a str. line

$\angle$ at a pt.

vert. opp. $\angle$

alt. $\angle$

corr. $\angle$

int. $\angle$

Types of Polygons

Sides	Polygon
3	Triangle
4	Quadrilateral
5	Pentagon
6	Hexagon
7	Heptagon
8	Octagon
9	Nonagon
10	Decagon

Polygon Angle Formulas

Sum of Interior Angles

$(n-2) \times 180°$

Sum of Exterior Angles

$360°$

Each Interior Angle (regular)

$\frac{(n-2) \times 180°}{n}$

Each Exterior Angle (regular)

$\frac{360°}{n}$

Problems In Real-World Contexts

Congruence & Similarity