# Section 5-8 The Law of Cosines. A b c C a B Solve ∆ABC if A= 120⁰, b=9, c=5.

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Section 5-8 The Law of Cosines

A b c C a B

Solve ∆ABC if A= 120⁰, b=9, c=5

=12.3

=39.3⁰

Solve ∆ABC if A= 105⁰, b=12, c=9 A 105⁰ 12 9 C a B

a 2 = b 2 + c 2 - 2bc cos ALaw of Cosines a 2 = 12 2 + 9 2 - 2(12)(9) cos 105° a 2 = 280.9049137 a= 16.76021819 So, a = 16.8. B = 43.6°. C = 180° - (105° + 43.6°) C = 31.4°

B = 43.6°. C = 180° - (105° + 43.6°) C = 31.4°

Solve ∆ABC if A= 105⁰, b=12, c=9 A 105⁰ 12 9 C a B

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