standard_description: Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles. For example, arrange three copies of the same triangle so that the sum of the three angles appears to form a line, and give an argument in terms of transversals why this is so.
problem_activity: Problem 3
Pre-unit
Match the pictures with the expressions.
A:
[IMG]
B:
[IMG]
C:
[IMG]
1: \(\hspace{1.5cm}6+2\)
2: \(\hspace{1.5cm}5+3\)
3: \(\hspace{1.5cm}8-3\)


aligns: no