Angles
What is an Angle?
An angle is formed when two rays share a common endpoint (vertex). Angles are measured in degrees (°), with a full circle measuring 360°.
45°
Vertex: The common endpoint where the rays meet
Rays: The two line segments that form the angle
Measure: The amount of rotation from one ray to another
Types of Angles
Acute Angle
Less than 90°
45°
Right Angle
Exactly 90°
90°
Obtuse Angle
Greater than 90° but less than 180°
135°
Straight Angle
Exactly 180°
180°
Angle Relationships
Complementary Angles
Two angles are complementary if their sum equals 90°.
30°
+
60°
=
90°
Supplementary Angles
Two angles are supplementary if their sum equals 180°.
120°
+
60°
=
180°
Vertical Angles
Vertical angles are formed when two lines intersect. Vertical angles are always equal.
a
b
b
a
a = a and b = b
Related Topics
Practice Angles
Test your knowledge with our interactive angle practice exercises.
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