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Mathematics LibreTexts

2.B: Other Triangle Properties

  • Page ID
    31442
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    Overview

    The purpose of this lesson is to identify and use other triangle properties.

    This lesson will address the following CCRS Standard(s) for Geometry:

    • 8.G.5: Use informal arguments to establish facts about the angle sum and exterior angles of triangles, above 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

    Directions

    1. Take notes while watching videos below
    2. Go to http://wamap.org and log into our course to complete assignment 2.B with 80% or better.

    Do

    Complete assignment 2.B with 80% or better at http://wamap.org

    Summary

    In this lesson we have learned:

    • Isosceles triangles have two congruent sides and two congruent angles
    • The sum of the angles of a triangle is 1800
    • The exterior angle of a triangle is equal to the sum of the opposite two angles
    • When combined, the two shortest sides of a triangle are longer than the third (longest) side
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