May 13, 2015

Prove theorems about triangles. Theorems include: measures of interior angles of a triangle sum to 180?; 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.

Exercises from Illustrative Mathematics

A set of exercises, commentary, and solutions. For this unit, choose:

G-CO Midpoints of Triangle Sides

G-CO Congruent angles in isosceles triangles

G-CO Sum of angles in a triangle

- Mathematics > General
- Mathematics > Geometry

- Grade 9
- Grade 10

Reason abstractly and quantitatively.

Construct viable arguments and critique the reasoning of others.

Use appropriate tools strategically.

Attend to precision.

Look for and make use of structure.

Prove theorems about triangles.