SOLUTION: If the sides of an ABC triangle are, a=5,b=6, and c=7, what is the value of angle C?

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Question 1197936: If the sides of an ABC triangle are, a=5,b=6, and c=7, what is the value of angle C?
Answer by math_tutor2020(3816) About Me  (Show Source):
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Law of Cosines
c^2 = a^2+b^2 - 2ab*cos(C)
7^2 = 5^2+6^2 - 2*5*6*cos(C)
49 = 61 - 60*cos(C)
cos(C) = (49-61)/(-60)
cos(C) = 0.2
C = arccos(0.2)
C = 78.4630409671846

Answer: Angle C is approximately 78.463 degrees