## ← 01-43 Trigonometry Review

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Showing Revision 1 created 06/27/2012 by Amara Bot.

1. Let's quickly review what we learned. Well first, we learned about similar triangles.
2. Two triangles are similar if their angles are identical
3. even though their sides don't have to be the same length.
4. And we've learned that these triangles have many special properties.
5. One really important property is that the ratio of side lengths are the same for two similar triangles.
6. What this means is that if I have a right triangle with a 40-degree angle here,
7. I can immediately tell you the ratio of this side to that side or this one to that one.
8. And that's a very powerful tool.
9. In fact, these ratios are so powerful that we gave names to them - sine, cosine, and tangent.
10. And we can remember what those names mean by SOH, CAH, TOA.
11. Sine is opposite over hypotenuse, cosine is adjacent over hypotenuse,
12. and tangent is opposite over adjacent.
13. Finally, we learned that we can go back and forth between sides and angles
14. and side lengths and angles or maybe even degrees.
15. And this is something that we'll be doing frequently throughout the course.
16. Let me say good work. This is a huge accomplishment learning this much already.
17. Now, let's put it to use and figure out what the circumference of the earth is.