6.1 An Introduction to Angles: Degree and Radian Measure
standard position:
OBJECTIVE 1: Understanding Degree Measure
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OBJECTIVE 2: Finding Coterminal Angles Using Degree Measure
Angles in standard position having the same terminal side are called coterminal angles.
Every angle (except an angle coterminal with 0 ) has a coterminal angle of least positive
measure. If  is a given angle, then use the notation C to denote the angle of least positive
measure coterminal with  .
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OBJECTIVE 3: Understanding Radian Measure
s
Definition
Radian
A radian is the measure of a central angle that has an intercepted arc
equal in length to the radius of the circle.
Relationship Between Degrees and Radians
360  2 radians
180   radians
  2


2
 

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Quadrant II
Quadrant III
Quadrant II
Quadrant III
Quadrant I
Quadrant IV
Quadrant I
Quadrant IV
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OBJECTIVE 4: Converting Between Degree Measure and Radian Measure
Converting Between Degrees and Radians
To convert degrees to radians, we use the conversion equation 1 

180
radians .
To convert radians to degrees, we use the conversion equation 1radian 
180


.
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OBJECTIVE 5: Finding Coterminal Angles Using Radian Measure
Do not write 
21 3

. These angles are coterminal but they are not equal.
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