HSG-CO.C.10
Prove theorems about triangles. Theorems include: measures of interior angles of a triangle sum to $180^\circ$; base angles of isosceles triangles are congruent; the segment joining midpoints of two sides of a triangle is parallel to the third side and half the length; the medians of a triangle meet at a point.
Tasks
Seven Circles I
Classifying Triangles
Finding the Area of an Equilateral Triangle
Midpoints of Triangle Sides
Congruent angles in isosceles triangles
Sum of angles in a triangle