standard_description: Derive using similarity the fact that the length of the arc intercepted by an angle is proportional to the radius, and define the radian measure of the angle as the constant of proportionality; derive the formula for the area of a sector.
problem_activity: Problem 1
Find all the angle measures that equal 127° and all the angle measures that are supplementary to 127°.
[IMG]
Problem 2
In the figure,
$${\overline{AB} \parallel \overline{CD}}$$
and
$${\overline{EF} \parallel \overline{GH}}$$
. Prove that
$${\angle AFE \cong \angle DKH}$$
.
[IMG]


aligns: no