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: The two triangles in the picture below are congruent:
[IMG]
a.   Give a sequence of rotations, translations, and/or reflections that take
$${\triangle PRQ}$$
to
$${\triangle ABC}$$
.
b.   Is it possible to show the congruence in part (a) using only translations and rotations? Explain.


aligns: no