Calculate cos(theta) to two decimal places.?

Please explain. Thank you!

cosine law is:
c^2 = a^2 + b^2 – 2abcosC So we have:
11^2 = 7^2 + 8^2 – 2(7)(8)cosC
121 = 49 + 64 – 112cosC
8 = 112cosC
-8/112 = cosC
cosC =~ -0.07

The Correct answer is 0.69.

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