SOLUTION: Find the largest angle, to the nearest tenth of a degree, of a triangle whose sides are 9cm, 12 cm and 18 cm.

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Question 292345: Find the largest angle, to the nearest tenth of a degree, of a triangle whose sides are 9cm, 12 cm and 18 cm.
Answer by Edwin McCravy(20064) About Me  (Show Source):
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Find the largest angle, to the nearest tenth of a degree, of a triangle whose sides are 9cm, 12 cm and 18 cm.

Use the law of cosines:

cos%28theta%29=%289%5E2%2B12%5E2-18%5E2%29%2F%282%2A9%2A12%29

cos%28theta%29=%2881%2B144-324%29%2F216

cos%28theta%29=%28-99%29%2F216

cos%28theta%29=-.4563333333

theta=%22117.2796127%B0%22

To the nearest tenth of a degree:

theta=%22117.3%B0%22

Edwin