8. Answer: (C) 101.3
Explanation:
Use the Law of Cosines:
c² = a² + b² - 2ab·cos C
28.2² = 16.9² + 19.5² - 2(16.9)(19.5)·cos C
795.24 = 285.61 + 380.25 - 659.1 cos C
795.24 = 665.76 - 659.1 cos C
129.38 = - 659.1 cos C
-0.196 = cos C
cos⁻¹ (-0.196) = cos⁻¹ (cos C)
101.3 = C
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10. Answer: (A) 27.9
Explanation:
Use the Law of Cosines:
c² = a² + b² - 2ab·cos C
c² = 25² + 18² - 2(25)(18)·cos 79
c² = 625 + 324 - 900 cos 79
c² = 949 - 171.7
c² = 777.3
√c² = √777.3
c = 27.9