Unit 2 · Core unit
Angle relationships that generate equations, and compass constructions that rely on equal radii rather than measurement.
What a strong answer looks like
A strong answer names the angle relationship being used, which is what turns a diagram into an equation.
Know
Complementary, supplementary, vertical, and linear-pair relationships each give an equation relating unknown measures.
Apply
Name the relationship, write the equation it implies, then solve.
Watch out
Assuming two angles that look equal are equal without a relationship justifying it.
Study move
Find an unknown angle using a named relationship and state the reason.
Know
A transversal across parallel lines makes corresponding and alternate interior angles congruent, and same-side interior angles supplementary.
Apply
Identify the angle pair type before deciding whether they are equal or sum to a straight angle.
Watch out
Applying a parallel-line result when the lines are not known to be parallel.
Study move
Find several angles from one known angle across a transversal.
Know
Compass and straightedge constructions work because arcs of equal radius create equal distances, not because anything was measured.
Apply
Justify a construction by naming which segments are equal by radius.
Watch out
Describing a construction as measuring, which misses why it is valid.
Study move
Construct a perpendicular bisector and explain why the result is perpendicular.
Modeling drill
Given one angle at a transversal across parallel lines, find every other angle and name the relationship used for each.
