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: Determine if the statement below is always, sometimes, or never true. Explain your reasoning.
“To prove two triangles similar, you need to prove that two of the corresponding sides are proportional.”


aligns: no