Thursday, June 05, 2008
Geometry (Class 88)
Lesson Title
Using the Law of Cosines
Overview
The warm-up for today’s class asks students to reflect on what they learned from the last class. The lesson for today provides many chances to clarify and apply the concepts and skills from the last class-- using the law of cosines to solve problems.
Textbook Sections
Supplemental
Vocabulary
center
inscribed angle
central angle
radius (pl: radii)
chord
diameter
sections of intersecting chords
extended chords
inscribe
cyclic quadrilateral
law of sines
apothem
oblique triangle
Key Attitudes
Math is about thinking creatively.
Key Ideas
The area of a triangle can be found using the Law of Sines
The Pythagorean Theorem can be “perfected” so that it can be sued with oblique as well as right triangles.
The sum of the two squares is smaller than the area of the third side when the included angle is obtuse and is larger when the included angle is acute.
The amount the Pythagorean Theorem needs to be adjusted depends on the size of the included angle and the lengths of the adjacent sides. (This implies the use of the cosine function.)
The amount the Pythagorean Theorem needs to be adjusted can be figured out using right triangle trigonometry.
In order to use the Law of Cosines, you need the measures of two sides and the included angle or the measures of all three sides of a triangle.
Key Skills
I can explain how and why the Pythagorean Theorem needs to be adjusted for oblique triangles.
I can use the Law of Cosines to solve for a missing side of a triangle.
I can use the Law of Cosines to solve for an angle in a triangle.
I can recognize a situation in which the Law of Cosines can be used.
Turn-In (#87)
End of Year Test A
Handouts
Chapter 13- Lesson 3: Warm-Up
Semester Grades: Corrections and Drops
Semester 2 Optional Review
Benchmark Test 6 Answers
Assignment
Benchmark Test 6
Grade Corrections and Drop Sheet (Due day of final)
Optional review (Due day of final)
Ch. 13 Lesson 3: Perfecting the Pythagorean Theorem: For an A-- ALL, B -> 10, C ->8
Disclaimer- The assignment as stated in class is the official assignment. Every effort is made to keep this posting accurate, but you should refer to what was stated in class as the final word.
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