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# Angles: introduction

Two rays that share the same endpoint form an angle. Learn about angles and the parts of an angle, like the vertex. Created by Sal Khan.

## Want to join the conversation?

• How are Angles used in everyday life?
• everywhere around you there is atleast more than one angle
• At , Sal says you can't call that angle A, then demonstrates another diagram. I know on the 2nd diagram that you can't call it H, but couldn't you call it A in the first one?
• Even Though it is an angle all by itself, the rule still applies.
• say that i wanted to name the angle BAC but i wanted name the reflex angle, how would i do it?
• you subtract 360 by the inside angel
• What is an angle? We jump directly into line arrays and segments and where angles are found but we have no clue of what an angle is at it's most basic explanation.
• An angle is a combination of two rays (half-lines) with a common endpoint. The latter is known as the vertex of the angle and the rays as the sides, sometimes as the legs and sometimes the arms of the angle.
• how many angles can you think of?
(1 vote)
• There are 15 types of angles: acute, right, complementary, oblique, obtuse, supplementary, reflex, straight, revolution and whole angles. Then when you have two parallel lines, there are more angles: corresponding, same side interior, same side exterior, alternate interior, and alternate exterior angles. There are many more that are similar but I won't go into those because they're so similar.
• why a right angle is ninety degrees?
• Each full circle is 360 degrees. A quarter of that would be a right angle, or 90 degrees.
• And pretend this isn't a greater than sign, but is this an angle? >
• Typically, we use the less than sign < to represent an angle. You can tell the difference between an angle and less than sign because angles will be indicated with letters (ex. <A).
• Is a vertex the meeting point between two rays or two line segments or two lines, or does it not matter?