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Geometry Course
Types of Angles - Part 2
Free Geometry Basics Course
Part 1
 Terms in Geometry
Part 2
 Types of Angles
Part 3
Part 4
Measuring Angles
Part 5
Bisectors, Congruencies, Theorems
Part 6
Transfersal Properties
Geometry Help
• Mathematicians Review
Conic Sections
• Pythagorean Theorem

 Related Resources
Measurement Formulas
Recommended Resources
Area Calculator
Introduction to Polygons


An angle is defined as: where two rays or two line segments join at a common endpoint called the vertex. See part 1 for additional information.

Acute Angle

An acute angle measures less that 90° and can look something like these (angles between the grey rays):

Right Angle

A right angle measures exactly 90° and will look something like this:

Obtuse Angle

An obtuse angle measures more than 90° but less than 180° and will look something like these:

Straight Angle

A straight angle is 180°

Reflex Angle

An reflex angle is more than 180° but less than 360° and will look something like this:

Pairs of Angles:

Complementary Angles
Two angles adding up to 90° are called complementary angles.

ABD + DBC are Complementary

Supplementary Angles
Two angles adding up to 180° are called supplementary angles.

ABD + DBC are Supplementary

If you know the angle of ABD, you can easily determine what the DBC is by subtracting ABD from 180!

On to Part 3.

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