← MATH 01310 · College Geometry
MATH 01310 · Proof & congruence/similarity
Similarity & proportions
Definition
Similar triangles have equal corresponding angles and proportional corresponding sides. AA is the usual similarity criterion. Side ratios create proportions for missing lengths.
Read this
Write correspondence carefully: △ABC ~ △DEF means AB/DE = BC/EF = CA/FD.
Parallel line in a triangle creates similar triangles (and intercept proportions).
Altitude to the hypotenuse in a right triangle yields three similar right triangles — classic proportion factory.
Drill with flashcards
Flip through these until you can say the answer before revealing it.
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Try this
Attempt each problem first, then open the worked solution.
1.Use AA to set up a proportion and solve for a missing side.