## Reflection: Discourse and Questioning Law of Cosines Day 1 of 2 - Section 1: Bell Work

I have looked up several definitions for the Law os Sines. Some definitions state that the Law of Sines is used only for oblique triangles, other just say the sides are in the ratio of ....

The text we use Larson, Precalculus with Limits, 2nd ed. states in the reading it is for oblique triangles but not in the definition. Another well known author Stewart states in "Precalculus Mathematics for Calculus, 5th ed.",p. 502 "The Law of Sines says that in any triangle the length of the sides are proportional to the sines of the corresponding opposite angles."

I think that it is best to allow students to use the Law of Sines with right triangles, but to encourage them to recognize that it may not be the most efficient method. One in a while, my students discover that because Sin (90 deg) = 1, the Law of Sines is a more general formula. Since this discovery is within their grasp, I leave this for my students to discover.

Can Law of Sines be used for Right Triangles
Discourse and Questioning: Can Law of Sines be used for Right Triangles

# Law of Cosines Day 1 of 2

Unit 6: Solving Problems Involving Triangles
Lesson 8 of 13

## Big Idea: How do you calculate the missing measurements of a triangle when you only know the 3 sides or 2 sides and the included angle?

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Standards:
Subject(s):
Math, Law of Cosines, triangles (Determining Measurements), Oblique Triangles, problem solving, pre
55 minutes

### Katharine Sparks

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