Types of Angles
A
Acute Angle
Less than 90° — e.g. 45°, 60°
R
Right Angle
Exactly 90° — found in squares and rectangles
O
Obtuse Angle
Between 90° and 180° — e.g. 120°, 150°
S
Straight Angle
Exactly 180° — a straight line
R
Reflex Angle
Between 180° and 360° — e.g. 270°, 300°
F
Full Rotation
Exactly 360° — a complete circle
Shape Angle Quick Reference
Triangle
3 sides • Interior angles sum = 180°
Square
4 sides • Interior angles sum = 360°
Pentagon
5 sides • Interior angles sum = 540°
Hexagon
6 sides • Interior angles sum = 720°
Formula
(n - 2) × 180° = sum of interior angles
Each Interior Angle
[(n - 2) × 180°] ÷ n (regular polygon)