Good Morning, Precalculus! To prepare for class: 1. Please find your DO NOW sheet and start today's DO NOW! Do Now: Find the semiperimeter of the triangle whose sides have lengths 32, 38 and 46. Then, find the measurements of the angles. (HINT: Use Law of Cosines to find the first angle measurement and go from there!)

Do Now: Find the semiperimeter of the triangle whose sides have lengths 32, 38 and 46. Then, find the measurements of the angles. (HINT: Use Law of Cosines to find the first angle measurement and go from there!)

Upcoming Assignments Due Wednesday 3/20: Hero's Law Practice Problems Worksheet (from yesterday - sheets are still at the front of the room) Due Thursday 3/21: Pg. 330 #7 and #9 For an extra challenge, try #3 Your Unit 10 Test will be next Tuesday, March 26!

Today's Agenda: 1. Do Now 2. Today's Objective 3. Hero's Formula 4. Work with a Partner 5. Unit 10, Obj. 3 Exit Slip

Today's Objective Unit 10, Objective 3: I will be able to calculate the area of a triangle using Hero's (Heron's) Formula. Section 5-8, pgs. 330

Hero's Law

Using the law of sines, we were able to find the area of a triangle when: 1. We knew two sides and their included angle 2. We knew at least two of the angles and one of the sides. Now, we can find the area of a triangle when we only know the lengths of all three sides. To do this: 1. Find the semiperimeter using the formula s = 1 (a+b+c), where a, b, and c are the lengths of the three sides. 2. Then, use Hero's Law:k = √s(s-a)(s-b)(s-c), where s is the semiperimeter of the triangle and a, b, and c are the lengths of the three sides. Hero's Law 2 A B C a b c

Work alone or with a partner to complete "More practice!"

Unit 10, Obj. 3 Exit Slip

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Unit 10, Obj. 3 Grade: 12 Subject: Precalculus Date: 3/19/2013

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