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## High school geometry

### Course: High school geometry>Unit 4

Lesson 2: Introduction to triangle similarity

# Triangle similarity review

Review the triangle similarity criteria and use them to determine similar triangles.

## What are the triangle similarity criteria?

AATwo pairs of corresponding angles are equal
Two triangles. One triangle is smaller than the other. Both triangle have two angles that are congruent.
SSSThree pairs of corresponding sides are proportional
Two triangles. One triangle is smaller than the other. The smaller triangle has side lengths a, b, and c. The larger triangle has side lengths a times k, b times k, c times k.
SASTwo pairs of corresponding sides are proportional and the corresponding angles between them are equal
Two triangles. One triangle is smaller than the other. The smaller triangle has side lengths a and b. The larger triangle has side lengths a times k and b times k. The angle between the side lengths of the smaller triangle is congruent to the angle between the side lengths of the larger triangle.

Problem 1
• Current
Three triangles labeled A, B, and C. Triangle A has a forty-six degree angle and a seventy-nine degree angle. Triangle B has a fifty-one degree angle and a sixty-two degree angle. Triangle C has a forty-six degree angle and a seventy-nine degree angle.
Which triangle is similar to triangle A?

Want to practice more problems like this? Check out this exercise for the AA criterion and this exercise for the SSS criterion.

## Want to join the conversation?

• i dont get most of this stuff
• Try to practice upon it and you might get it, or just use khan academy's practice a lot. Hope it helps
• How can you tell the difference between SAS and SSA? (Assume you had a problem and had to chose if it was sim. because of SAS or SSA, how would you figure it out?)
• SAS means that the angle is in between the two sides in question. SSA means the angle is not in between.
• The videos im watching is not adding up to the working you guys are giving me. Im so lost.
• Define Equation
• An equation is a statement with an equals sign.

So 3 + 5 = 8 and 5x + 12 = (x / 4) + 3 are both equations,
but 24 * 9 and 3y ≥ x - 8 are not equations.
• why does this make sense
• Because it just does.
• What other triangle similarity criteria can be used?
(1 vote)
• gelp im in 8 doing this while other people are doing calculus rn :sob:
(1 vote)
• Yo, man. This is how we do da thing. Firstly, if the triangles have 2+ matching corresponding angles, then it is similar. If it has side lengths that can be divided by a number, say X, and then match the side lengths of your other triangle, then it is similar. If it has 2 matching corresponding(see last sentence) sides, and the angle between these is the same, then it is similar. -Beauregard42. If this helps you, your welcome.