Sections:

Law of Sines and Law of Cosines, Page 13

Law of Cosines: Examples (continued)

What if you are given the three sides of the triangle?

Example 2:

Given triangle ABC, with a = 5, b = 6, and c = 8, solve the triangle (round to the nearest tenth). 

5.2.14 graphic 1

Find A:

a^2 = b^2 + c^2 - 2bc cos A; 5^2 = 6^2 + 8^2 - 2(6)(8) cos A; 25 = 36 + 64 - 96 cosA; A = 38.6 degrees

Find B:

b^2 = a^2 + c^2 - 2ac cos B; 6^2 = 5^2 + 8^2 - 2(5)(8) cosB; 36 = 89 - 80 cosB; -53 = -80 cosB; B = 48.5 degrees

Find C:

the measure of angle C = 180 - (38.6 + 48.5) = 92.9 degrees