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 * **Aim: What is the Law of Sines and how can we apply it?** //(This formula is on your Regents Reference Sheet)//

At the end of this lesson, you will be able to...
 * 1) express the Law of Sines in different forms
 * 2) explain the conditions necessary to apply the Law of Sines
 * 3) apply the Law of Sines to find the length of a side of a triangle, if measures are given for two angles and a side
 * 4) justify whether or not a triangle is acute, obtuse or right
 * 5) solve problems involving the use of the Law of Sines

The Law of Sines is a formula that allows you to find the missing sides or angles from a triangle.

Copy the questions into your notebook and answer them as you watch the video.


 * 1) What is the formula for the Law of Sines?
 * 2) How many ratios do you need to use to solve for a missing part of a triangle?
 * 3) What is an oblique triangle?
 * 4) What are the requirements to solve this type of triangle?
 * 5) What relationships are we using today?
 * 6) Which one did James say was going to be discussed in another video?

[|Video 1]

[|Video 2]

As you've seen in both videos, you can solve for the variable first as in Video 1, or you may use cross-products to solve as in Video 2.


 * **Classwork:** Solve each problem. Be sure to follow directions. Draw a picture for each.

1. In triangle ABC, c= 12, the measure of angle B = 120, and the measure of angle C = 45. Find the //exact value// of side b. (Side b = 6sqrt6)

2. In triangle DEF, the measure of angle D = 50, the measure of angle E = 95, and f = 12.6. Find d to the //nearest tenth//. (side d= 16.8)


 * **Homework:** #3-21 odd

[|Law_of_Sines_1.JPG]

[|Law_of_Sines_2.JPG]


 * **Answers**

[|A-Law_of_Sines.JPG]


 * **Journal entry:** Ptolemy was aware of the Law of Sines in the 2nd century BC. Use the Internet to find out how the Greeks used this theorem.