This week in advanced math we learned how to do law of cosines. This law is used when you don’t have a pair in a non-right triangle.
The formula for solving for law of cosine is (opposite leg) ^2= (adjacent leg) ^2+ (adjacent leg) ^2-2(adjacent leg) (adjacent leg) cosine (angle between).
Example: problem dealing with the law of cosine.
Suppose 2 sides of a triangle have lengths 3cm and 7cm and the angle between their measures is 130 degrees. Find the 3rd side.
1. You do x squared=7squared+3squared-2(3) (7)Cos 130 degrees
2. Everything is squared so when you plug it all into your calculator you must square root all of it.
3. You get 9.219
4. 9.219 is your 3rd side.
The entire chapter was about solving all kinds of different triangles. Law of Cosines was one of the easiest sections in chapter 9. You use law of cosines when you cannot use SOHCAHTOA or law of sines. All you have to do to solve the triangle is plug in the formula:
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