Geometry 5-7 Primer: The Hinge Theorem

By Matt Richardson
Last updated about 3 years ago
5 Questions
Interact with the applet for a few minutes before responding to the item below.

Explore: Which of the elements of the triangles in the applet can be modified? Which cannot be modified?

  • AB
  • BC
  • CA
  • DE
  • EF
  • FD
  • m∠A
  • m∠D
  • location of △ABC
  • location of △DEF
  • Can be modified
  • Cannot be modified
For your convenience, the same applet is embedded below.

Set the applet such that m∠A ≠ m∠B and respond to the items that follow.

Exploration: In your current configuration, which angle has the greater measure?

Extension: What conclusion(s) can you make about the relationship between the included angle measures and the third side lengths?

Exploration: In your current configuration, which side length has the greater measure?

Extension: The properties you explored apply to all pairs of triangles with two sets of congruent sides and non-congruent included angles. This property is expressed in the Hinge Theorem. Fill in the blank to complete the theorem.

If two sides of one triangle are congruent to two sides of another triangle, and the included angles are not congruent, then the longer third side is opposite the __?__ included angle.