SOLUTION: If AB = 10, BC = 9, and CA = 11, name the largest angle of ∆ABC.

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Question 732070: If AB = 10, BC = 9, and CA = 11, name the largest angle of ∆ABC.
Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!

The largest side is opposite the largest angle.

The largest side is AC which is 11.
The angle opposite AC is ∠B (which you may give as ∠ABC or as ∠CBA)

That may be all you are asked to find. But in case you have
studied the law of cosines, I will continue to find the measure of
∠B just in case:

To find the measure of ∠B we use the law of cosines:

cos(∠B) = %28a%5E2%2Bc%5E2-b%5E2%29%2F%282ac%29

cos(∠B) = %289%5E2%2B10%5E2-11%5E2%29%2F%282%2A9%2A10%29

cos(∠B) = %2881%2B100-121%29%2F180 

cos(∠B) = 60%2F180

cos(∠B) = 1%2F3 

Use the inverse cosine feature of your calculator:

m∠B = 70.52877937°

Edwin