Lesson 1 of 14
SAS: two sides and the angle between
Show on a big screenTwo triangles are drawn separately from the same measurements. Will they match?
The rule
Yes, these two match, because the angle sits between the two sides.
A criterion is a set of measurements that fixes one triangle. Fixing one triangle means every triangle built from those measurements is congruent. SAS is a criterion. It means side, angle, side. The angle must sit between the two sides.
Take sides 7 and 5 with 55° between them. Draw it twice. The two drawings fit exactly on each other.
| Name | Known parts | Fixes one triangle? |
|---|---|---|
| SAS | two sides and the angle between | Yes |
| SSS | three sides | Yes |
| ASA | two angles and the side between | Yes |
| SSA | two sides and an angle not between | Not always |
| AAA | three angles | No |
Three angles give the shape, not the size. A small and a big triangle can share them.
Look at the thick parts. Name the rule they give.
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Try the lab to finish this lesson.