SOLUTION: Find the largest angle in a triangle with sides 6.0 cm, 7.0 cm and 8.0 cm.

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Question 1169134: Find the largest angle in a triangle with sides 6.0 cm, 7.0 cm and 8.0 cm.
Answer by ikleyn(52903) About Me  (Show Source):
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The largest angle is opposite to the longest side, which is 8 cm long.


Use the Cosine law

    8^2 = 6^2 + 7^2 - 2*6*7*cos(x)


From this equation,

    cos(x) = %286%5E2+%2B+7%5E2+-+8%5E2%29%2F%282%2A6%2A7%29 = 0.25.


Therefore,  x = arccos(0.25).


Use your calculator.

Solved.