Education Technology

Geometry: Interior & Exterior Angles of a Triangle
by Texas Instruments

Published on February 15, 2011


Students measure interior and exterior angles of a triangle and make conjectures about their relationships.

Key Steps

  • Image

    Students should construct a triangle using the Triangle tool and label the vertices A, B, and C.

  • Image

    With Cabri™ Jr., students construct a triangle and measure the three interior angles. With the Calculate tools they make a conjecture about the sum of the angles for all triangles, acute, obtuse, and right.

  • Image

    Using the triangle students have already constructed, they will construct a line and measure the exterior angle that results from it. Using the Calculate tool again, they will make conjectures about the relationships between interior and exterior angles.