Radian Measure of Angles - Concept   An angle is the figure
formed by two rays with a common endpoint. We typically use
degree measures when measuring angles, however we can use radian
angle measure as an alternate way of measuring angles in
advanced math courses. This measure is based on using a point on
the vertex and measuring the arc length compared to the radius.
I want to talk about radian measure of angles. Recall that an
angle is the figure formed by 2 rays with a common end point.
I've drawn 2 rays here, ray ba and ray bc and they share end
point b and this figure is called an angle. Now you may remember
from Geometry that degree measure is how we normally measure
angles in the real world 360 degrees is one revolution of the
circle that definition results in the following definitions for
acute angle, right angle and obtuse angle. And acute angle is an
angle between 0 degrees and 90 degrees, a right angle is an
angle with a measure of exactly 90 degrees and an obtuse angle
is an angle between 90 deg