SOLUTION: What is the approximate measure of angle C in a triangle with a = 21, b = 14, and c = 28?

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Question 474554: What is the approximate measure of angle C in a triangle with a = 21, b = 14, and c = 28?
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
first let's use law of cosines
cos+C+=+%28+21%5E2+%2B+14%5E2+-+28%5E2+%29+%2F+%282+%2A+21+%2A+14%29
cos+C+=+%28+441+%2B+196+-+784+%29+%2F+588
cos+C+=++-147%2F588
cos+C+=++-0.25


The inverse function of cosine.
Basic idea: To find cos-1 (-0.25), we ask "what angle has cosine equal to -0.25?"
The answer is:
C+=+104.5 °