3.1 Radian
Measure
Radian
An angle with its vertex at the center of a circle that intercepts an
arc on the circle equal in length to the radius of a circle has a measure of 1
radian
Converting Between Degrees and
Radians
Convert
an angle in degree measure to radian measure
a)
108o
b) -135o
c)
325.7o
Convert
each angle in radian measure to degree measure
a) 
b)
c)
-2.92
[Note: To convert from radians to
degrees, if the radian measure contains π, one could substitute 180o
for π]
**Agreement
on Angle Measurement Unit
If no unit of measure is
specified, then the angle is understood to be measured in radians.
Common
Radian and Degree Equivalences
|
Degrees |
Radians |
Radians |
|
|
Exact |
Approximate |
|
0 |
0 |
0 |
|
30 |
|
.52 |
|
45 |
|
.79 |
|
60 |
|
1.05 |
|
90 |
|
1.57 |
|
180 |
|
3.14 |
|
270 |
|
4.71 |
|
360 |
|
6.28 |
The
equivalences in the above diagram are used frequently. Much time can be saved from converting, if
you just learn them!!
Finding
Trig Function values of angles in radian measure
a) 
b) 
c) 
d) 