### Video Transcript

Find the measure of angle
πΆπ΄π΅.

First, we wanna list out the
information weβre given in this diagram. We can say that line segment π·πΆ
is equal to line segment π΄πΆ, which is equal to line segment π·π΄. Then, the line π΄π΅ is tangent to
the circle at point π΄. Using this information, we want to
know the measure of angle πΆπ΄π΅. From the first two given
statements, there are some conclusions we can draw. First, we can say that triangle
π΄πΆπ· is equilateral. Since we know that this is an
equilateral triangle, we can say that all three interior angles will measure 60
degrees. But to go any further, we need to
remember the alternate segment theorem.

The alternate segment theorem tells
us that the angle between a tangent and a chord is equal to the angle in the
alternate segment. Our angle, angle πΆπ΄π΅, is the
angle between a tangent and a chord. And it will be equal to this angle
in the alternate segment. And so we would say that the
measure of angle πΆπ΄π΅ equals 60 degrees by the alternate segment theorem.