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Mathematics LibreTexts

1.C: Proportions and Similar Polygons

  • Page ID
    31436
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    Overview

    The purpose of this lesson is to use properties of similar polygons and proportions to find unknown measures.

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

    • 7.G.1: Solve problems involving scale drawings of geometric figures, including computing actual lengths and areas from a scale drawing and reproducing a scale drawing at a different scale
    • 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 1.C with 80% or better.

    Do

    Complete assignment 1.C with 80% or better at http://wamap.org

    Summary

    In this lesson we have learned:

    • Given the proportion LaTeX: \frac{a}{b}=\frac{c}{d}, we can solve by multiplying diagonals to get ad = bc.
    • If to polygons are similar, then corresponding sides are proportional
    • If two angles of one triangle are congruent to two angles of another triangle, then the triangle's sides are proportional.
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