Law of Cosines



1. Using the given information: [pic]to solve the triangle.

If you tried to use the Law of Sines, explain what happened? What combination of sides and angles do you have in the example above? (AAS, SAS, etc…)

To solve triangles when given SSS or SAS, you will need to use the __________________________.

LAW OF COSINES:

2. Try using the Law of Cosine instead: [pic] (how does this look familiar?)

Solve for all parts of the triangle from problem number 1.

Keeping it all organized!

|Given: |AAS or ASA or SSA |SAS or SSS |

|USE: | | |

Practice: Solve for the missing measurements in each triangle. ROUND TO NEAREST THOUSANDTH. (Remember, if you are looking for an angle, you need to use an inverse!)

4. [pic]; [pic], b=12

5. [pic]; b=5, c=7

6. [pic]

7.) A = 56°, c = 13, b = 9

8.) B = 94°, a = 12, c = 15

9.) a = 12, b = 7, c = 10

10.) a = 33, b = 27, c = 20

Change answers to nearest thousandth!

Answers!

4.) B = 41°, c = 16.58, a = 17.24 8.) A = 37.09°, C = 48.91°, b = 19.11

5.) B = 32.05°, C = 47.95°, a = 9.28 9.) A = 87.95°, B = 35.66°, C = 56.39°

6.) A = 63.26°, C = 64.74°, c = 34.43 10.) A = 87.88°, B = 54.85°, C = 37.27°

7.) B = 43.01°, C = 80.99°, a = 10.92

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Unit 9 Day 6: Law of Cosines (LOC)

Date _________ Period_________

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