TT-4+Law+of+Cosines

**NOTE: BEFORE READING ABOUT THE __LAW OF COSINES__ PLEASE READ ABOUT THE LAW OF SINES
More About the Law of Cosines! [] [] []

What is the Law of Cosines? In this section you will learn how to solve a triangle using the Law of Cosines and the equations listed below. You may also refer to your textbook (pages 417-423, Chapter 6.2). When can you use the law of cosines? You use it to solve for any triangle whether it be right, acute or obtuse. You can only use the Law of Cosines when you have SAS or SSS. After you find one of the three missing dimensions, you can use Law of Sines to solve the rest of the triangle.

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When to use these equations: **Standard form** equations are used to find the missing side length of your triangle. Plug your givens into one of the three equations and find the missing side.

**Alternative form** equations derive from the __standard form equation__. The equation is rearranged so that you can find any of the missing angles you need.

**Heron's Area Formula** is used to find the area of a triangle when you only have the side lengths. You must first find //s// and then plug the remaining side lengths into the area formula.

Here are some problems you can try on your own!
Example 1: a= 8 feet b= 19 feet c=14 feet. Solve triangle ABC.

Example 2: measure of angle B= 75 degrees, a= 20, c= 18. Solve Triangle ABC

Example 3: a= 6, b= 8, c= 12. Solve triangle ABC

Example 4: b= 16, a= 12, and c= 18. Solve triangle ABC

media type="file" key="Midterm Math Review.mov" align="center" __**Answer to example problems:**__ Example 1: measure of angle B= 116.8 degrees measure of angle C= 41.1 degrees measure of angle A= 22.1 degrees Example 2: measure of angle C= 48.6 degrees measure of angle A= 56.4 degrees b= 23.19 Example 3: Measure of angle C= 117.3 degrees measure of angle B= 36.3 degrees measure of angle A= 26.4 degrees Example 4: measure of Angle A= 40.8 degrees measure of angle B= 60.6 degrees measure of angle C= 78.6 degrees