ACT Preparation / Unit 13 ACT 1219 short lesson, about 20 seconds
Similar Triangles
Captions available
The idea
Similar triangles have equal corresponding angles and proportional corresponding sides. Two pairs of equal angles, the AA test, are enough to prove similarity.
In practice
Triangles with sides 3, 4, 5 and 6, 8, 10 are similar, with a ratio of 2.
Where people slip
Match sides by the angles they face, not by position on the page.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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