http://www.ck12.org Chapter 7. Similarity
Example C
IsDE||CB?
Use the Triangle Proportionality Converse. If the ratios are equal, then the lines are parallel.
6
18 =
1
3 and
8
24 =
1
3
Because the ratios are equal,DE||CB.
Watch this video for help with the Examples above.
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CK-12 Foundation: Chapter7TriangleProportionalityB
Vocabulary
A line segment that connects two midpoints of the sides of a triangle is called amidsegment. A midpoint is a point
that divides a segment into two equal pieces. Pairs of numbers areproportionalif they are in the same ratio.
Guided Practice
Use the diagram to answers questions 1-5.DB‖F E.
- Name the similar triangles. Write the similarity statement.
2.BEEC=FC?
3.ECCB=CF?
4.DB? =BCEC
5.FCFC+?=F E?
Answers:
- 4 DBC∼4F EC
- DF
- DC
- FE
- DF; DB
Practice
Use the diagram to answer questions 1-5.AB||DE.
- FindBD.
- FindDC.
- FindDE.