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Chapter 6 Investigating Non-Right Triangles as Models for Problems: 6.6 Adjusting the Pythagorean Theorem: The Cosine Law. 6.6 Adjusting the Pythagorean Theorem: The Cosine Law. Goal for Today: Learn about and apply the cosine law. 6.6 Adjusting the Pythagorean Theorem: The Cosine Law.
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Chapter 6 Investigating Non-Right Triangles as Models for Problems: 6.6 Adjusting the Pythagorean Theorem: The Cosine Law
6.6 Adjusting the Pythagorean Theorem: The Cosine Law Goal for Today: • Learn about and apply the cosine law
6.6 Adjusting the Pythagorean Theorem: The Cosine Law *The same holds true for any triangle Ex. XYZ *The same pattern holds true for any triangle for example, triangle XYZ
6.6 Adjusting the Pythagorean Theorem: The Cosine Law • The cosine law is used to find the 3rd side of a triangle when 2 sides and a contained angle are known, or • To find an angle when the length of 3 sides are known
6.6 Adjusting the Pythagorean Theorem: The Cosine Law • 2 sides and a contained angle… ex. 1 A 7cm ? 43⁰ B C 5cm
6.6 Adjusting the Pythagorean Theorem: The Cosine Law A 7cm ? 43⁰ B C 5cm
6.6 Adjusting the Pythagorean Theorem: The Cosine Law • 3 sides and finding an angle… ex. 2 A 7cm 4.8 ? B C 5cm
6.6 Adjusting the Pythagorean Theorem: The Cosine Law • 3 sides and finding an angle… ex. 2 ?
6.6 Adjusting the Pythagorean Theorem: The Cosine Law A 7cm 4.8 B C 5cm
Homework • Tuesday, January10th - Hwk6.6 Cosine Law Hwk p.566, #2-10, 12a, 13ac
6.6 Adjusting the Pythagorean Theorem: The Cosine Law • Ex. 1 A bicycle race follows a triangular course. The three legs of the race are, in order, 2.3km, 5.9km, and 6.2km. Find the angle between the starting leg and the finishing leg to the nearest degree.
6.6 Adjusting the Pythagorean Theorem: The Cosine Law Ex. 1 2.3km P Q ? 6.2km 5.9km R
6.6 Adjusting the Pythagorean Theorem: The Cosine Law • Ex. 2 The radar screen of an airport control tower shows that two plans are at the same altitude. According to the range finder, one plane is 100 km away, in the direction N60°E. The other is 160km away, at a direction of S50°E. How far apart are the two planes?
6.6 Adjusting the Pythagorean Theorem: The Cosine Law N B Ex. 2 N60°E 60° 100km C 160km 50° S50°E S A
6.6 Adjusting the Pythagorean Theorem: The Cosine Law • Ex. 2… In order to find how far apart the two planes are, we first have to find out the angle opposite the side of the line between the two planes that will be the third side of the triangle… • We can use the supplementary angle rule… • Angle BCA = 180°- 60°- 50°= 70°
Homework • Thursday, January 9th-