Chapter 3, Section 3.1 – Radian Measure
There are several different ways to measure angles, just as there are different ways to measure length. One way to measure angles is in radians, and it is
especially useful in advanced mathematics.
; The measure of a central angle θ that intercepts
an arc s equal in length to the radius r of the
What is the radian measure of the entire unit circle?
Converting Between Degrees and Radians
360？ = 2 radians or 180？ = radians ；；
1？ = radians, or 1 radian =
1. Multiply a radian measure by and simplify to
convert to degrees.
2. Multiply a degree measure by and simplify
to convert to radians.
Example: Convert each degree measure to radian.
a. 45？ b. 30？ c. 210？
d. 720？ e. 249.8？ f. 53？40’
Example: Convert each radian measure to degrees.
b. c. a.
d. e. 4.25 f. -3.2
Finding Function Values for Angles in Radians
Example: Find each of the following functions:
a. tan = ________ b. csc = __________
3ππ，(，(c. cot= ________ d. sin;= ________ ;！；！；