Names of Angles
As the Angle Increases, the Name Changes
Type of Angle | Description | |
---|---|---|
Acute Angle | an angle that is less than 90� | |
Right Angle | an angle that is 90� exactly | |
Obtuse Angle | an angle that is greater than 90� but less than 180� | |
Straight Angle | an angle that is 180� exactly | |
Reflex Angle | an angle that is greater than 180� |
Be Careful What You Measure
This is an Obtuse Angle. | And this is a Reflex Angle. |
But the lines are the same ... so when naming the angles make sure that you know which angle is being asked for! |
Parts of an AngleThe corner point of an angle is called the vertexAnd the two straight sides are called arms The angle is the amount of turn between each arm. |
Labelling Angles
There are two main ways to label angles: 1. by giving the angle a name, usually a lower-case letter like a or b, or sometimes a Greek letter like a (alpha) or ? (theta) 2. or by the three letters on the shape that define the angle, with the middle letter being where the angle actually is (its vertex). Example angle "a" is "BAC", and angle "?" is "BCD" |
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