Unit 4 - Objective 1 - Angles


An angle is formed by two rays that have the same endpoint.  This common endpoint is called the vertex of the the angle and  the two rays are called the sides of the angle.

u4obj101.gif (2490 bytes)

Angles may be measured using degrees or radians.  If the rotation of the terminal side from the initial side is counterclockwise, the angle is positive.   If the rotation is clockwise, the angle is negative.

Examples:

u4obj102.gif (5037 bytes)

 

 

If there is no degree symbol () after the angle measure, then assume that it is a radian measure.  Each degree is divided into 60 minutes and each minute into 60 seconds.  The symbol ' is used for minutes and " for seconds.   So 60' = 1 and 60"=1'.  In decimal degrees:

15' = (15/60) = 0.25 and 27" = (27/3600) = 0.0075

 

 


Conversion between Degrees and Radians

Examples:

1.

 

1 radian = 1 (180/p) appro2_g.gif (178 bytes) 180/3.1416 appro2_g.gif (178 bytes) 57.296
or
appro2_g.gif (178 bytes) 57

2.
1 = 1 (p/180) appro2_g.gif (178 bytes) 3.1416/180 appro2_g.gif (178 bytes) 0.01745 radians

3.
p/4 radians = p/4 (180/p) = 180/4 = 45

4.
60 = 60 (p/180) = p/3 radians

 


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Copyright 1996 by B. Chambers and P. Lowry. All Rights Reserved.