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: Using the diagram below:
[IMG]
What can be concluded about the relationship between line
$$l$$
and plane
$$P$$
? Why?
What can be concluded about the relationship between planes
$$P$$
and
$$Q$$
? Why?
What can be concluded about the relationship between lines
$$l$$
and
$$m$$
? Why?
What can be concluded about
$$\overline{AB}$$
and
$$\overline{CD}$$
?
Line
$$j$$
lies in plane
$$P$$
, and line
$$i$$
lies in plane
$$Q$$
. What can be concluded about the relationship between lines
$$i$$
and
$$j$$
?


aligns: no