SOLUTION: Hi I have another question I would like to verify my answer to: In Δ ABC, find the value of ∠C, if a = 5.7 m, b = 3.9 m, and c = 7.7 m. answer : C=105 degrees

Algebra ->  Trigonometry-basics -> SOLUTION: Hi I have another question I would like to verify my answer to: In Δ ABC, find the value of ∠C, if a = 5.7 m, b = 3.9 m, and c = 7.7 m. answer : C=105 degrees       Log On


   

Question 483793: Hi I have another question I would like to verify my answer to:
In Δ ABC, find the value of ∠C, if a = 5.7 m, b = 3.9 m, and c = 7.7 m.
answer : C=105 degrees

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!


Use the law of cosines

cos%28C%29=%28a%5E2%2Bb%5E2-c%5E2%29%2F%282ab%29

cos%28C%29=%285.7%5E2%2B3.9%5E2-7.7%5E2%29%2F%282%285.7%29%283.9%29%29

cos%28C%29=%2832.49%2B15.21-59.29%29%2F44.46

cos%28C%29=%28-11.59%29%2F44.46

cos%28C%29+=+-.2606837607

Use the inverse cosine function on your calculator,
being sure it is in degree mode, not radian mode.

C+=+%22105.1106379%B0%22

to the nearest whole degree is 105°

Edwin