6.4 Radians, Arc Length, and Angular Speed

Find points on the unit circle determined by real numbers.

Convert between radian measure and degree measure; find coterminal, complementary, and supplementary angles.

Find the length of an arc of a circle; find the measure of a central angle of a circle.

Convert between linear speed and angular speed.
Another useful unit of angle measure is called a radian. To introduce radian measure, we use a circle centered at the origin with a radius of length 1. Such a circle is called a unit circle. Its equation is $x{\text{\hspace{0.05em}}}^{2}+y{\text{\hspace{0.05em}}}^{2}=1$.
Distances on the Unit Circle
The circumference ...
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