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6.2 law of cosines.notebook February 27, 2018

Section 6.2 Law of Cosines

Objective: Given an oblique triangle (has no right angles) students will be able to find all the missing sides and angles.

Study Problems

Page 441 #1, 3,17, 19, 25, 26

Warm Up

The course for a boat race starts at point A and proceeds in the direction S 52o W to point B, then in the direction S 40o E to point C, and finally back to A. The point C lies 8 km directly south of point A.  Approximate the total distance of the race course. 

6.2 law of cosines.notebook February 27, 2018

To solve an oblique triangle, you need to know:

1. Two angles and any side(AAS or ASA)

2. Two sides and an angle opposite one of them(SSA)

3. Three sides

4. Two sides and their included angle (SAS)

Given 3 sides of a triangle, how do we know it forms a triangle?

Are there restrictions on SAS to form a triangle?

6.2 law of cosines.notebook February 27, 2018

Law of CosinesStandard Form Alternative Form

ExampleFind three angles of a triangle with side lengths of a=8 ft, b=19 ft and c=14 ft.

6.2 law of cosines.notebook February 27, 2018

ExampleFind the remianing angles and side of a triangle with side lengths of b=15 cm, c=10 cm and angle A=115o.

6.2 law of cosines.notebook February 27, 2018

Example

Find the area of the triangle region having sides of lengths a=43 meters. b=53 meters and c=72 meters.