http://www.ck12.org Chapter 7. Similarity
7.8 Triangle Proportionality
Here you’ll learn how to apply both the Triangle Proportionality Theorem, which states that if a line that is parallel
to one side of a triangle intersects the other two sides, then it divides those sides proportionally.
What if you were given a triangle with a line segment drawn through it from one side to the other? How could you
use information about the triangle’s side lengths to determine if that line segment is parallel to the third side? After
completing this Concept, you’ll be able to answer questions like this one.
Watch This
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Click image to the left for more content.CK-12 Foundation: Chapter7TriangleProportionalityA
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Click image to the left for more content.James Sousa:Triangle Proportionality Theorem
MEDIA
Click image to the left for more content.James Sousa:Using the Triangle Proportionality Theorem to SolveforUnknownValues
Guidance
Think about a midsegment of a triangle. A midsegment is parallel to one side of a triangle and divides the other two
sides into congruent halves. The midsegment divides those two sidesproportionally.
Investigation: Triangle Proportionality
Tools Needed: pencil, paper, ruler