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### Course: Congruence, Similarity, Right Triangles, & Trig 241+ > Unit 4

Lesson 2: Intro to triangle similarity- Intro to triangle similarity
- Triangle similarity postulates/criteria
- Angle-angle triangle similarity criterion
- Determine similar triangles: Angles
- Determine similar triangles: SSS
- Determining similar triangles
- Prove triangle similarity
- Triangle similarity review

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# Triangle similarity review

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

## What are the triangle similarity criteria?

AA | Two pairs of corresponding angles are equal | |

SSS | Three pairs of corresponding sides are proportional | |

SAS | Two pairs of corresponding sides are proportional and the corresponding angles between them are equal |

*Want to learn more about the triangle similarity criteria? Check out this video.*

## Check your understanding

*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(29 votes)
- Try to practice upon it and you might get it, or just use khan academy's practice a lot. Hope it helps(23 votes)

- 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?)(12 votes)
- SAS means that the angle is in between the two sides in question. SSA means the angle is not in between.(22 votes)

- The videos im watching is not adding up to the working you guys are giving me. Im so lost.(14 votes)
- 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.(9 votes)
- 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.(13 votes)

- What other triangle similarity criteria can be used?(3 votes)
- I believe AA, SAS, and SSS are the only triangle similarity theorems(6 votes)

- I thought I thought I would need a calculator for quiz 1,

But I got a 100% Without even trying.

*And I never did this before!*(5 votes) - Couldn't ASA also work?(2 votes)
- erm, well ok ASA shows that two triangles are congruent which means they are similar. However, if you want two similar triangles that are not congruent then ASA does not work.(5 votes)

- These lessons do not explain SSS similar triangles very well. What lesson would help me understand the basics?(2 votes)
- I suppose trying the Triangle Similarity postulates/criteria lesson, or going back and reading the articles and doing all of the practice problems may help you. Ultimately, in summary, the SSS similarity is used when every side can be multiplied by a constant to get the new side, for example, if AB/XY was 4, AC/AZ was 4, and BC/YZ was 4, it would be a SSS similarity because each value can be multiplied either by 4 or 1/4 (depending on which number is larger) which is defined as the constant. I hope this helps!(4 votes)

- i don't get it sometimes(3 votes)
- Is there anything I can do to help you?(2 votes)