All About Angles

Angles, Triangles and Transversal Lines

By Dean Lollis

Key definitions

• Angle: Formed by two rays (lines) the same endpoint.

• Triangle: A shape with three sides and three interior angles

• Transversal Lines: A line that crosses at least two other lines

Multiple Choice

Two rays that meet at a common end point are called an...

• point

• line

• angle

• line segment

Types of Angles

• Acute: Angles that measure less than 90 degrees.

• Obtuse: Measures greater than 90 degrese

• Right angle: Measures exactly 90 degrees

• Straight: Measures 180 degrees

Types of Angles

• Complementary Angle: Two angles with a sum of 90 degrees

• Supplementary Angle: Two angles whose sum is 180 degrees

Angles formed by two intersecting lines that are opposite each other. They have the same measure.

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1 & 3 are vertical angles. So are 2 & 4​

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Vertical Angles

Angles that are related because they share the same measure.

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In this picture, angles A & D are congruent. So are B & E and ​F & C.

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​Congruent Angles