1. Mrs. Rivas International Studies Charter School. The Law of Cosines and its Derivation The Law of Cosines is used to solve triangles in which two sides and the included angle (SAS) are known, or those in which three sides (SSS) are known.

2. Mrs. Rivas International Studies Charter School. The Law of Cosines and its Derivation Using the right triangle that contains angle A, we apply the definitions of the cosine and the sine.

3. Mrs. Rivas International Studies Charter School. The Law of Cosines and its Derivation The resulting equation is one of the three formulas for the Law of Cosines. The other two formulas are derived in a similar manner.

4. Mrs. Rivas International Studies Charter School. Solving Oblique Triangles

5. Mrs. Rivas International Studies Charter School. Step 1 Use the Law of Cosines to find the side opposite the given angle. Thus, we will find a.

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7. Mrs. Rivas International Studies Charter School. Step 3 Find the third angle. Subtract the measure of the given angle and the angle found in step 2 from 180°.

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11. Mrs. Rivas International Studies Charter School. Step 3 Find the third angle. Subtract the measures of the angles found in steps 1 and 2 from 180°.

12. Mrs. Rivas International Studies Charter School. Solution Solution After two hours, the plane flying at 325 miles per hour travels 325  2 miles, or 650 miles. Similarly, the plane flying at 300 miles per hour travels 600 miles

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14. Mrs. Rivas International Studies Charter School. Heron’s Formula

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16. Mrs. Rivas Check Points 1-4 Check Points 1-4 and Pg. 661# 2, 4, 6, 10- 18 Even 26, 30, 32, 40, 42