A triangular parcel of ground has sides of length 730 feet 6

A triangular parcel of ground has sides of length 730 feet, 655 feet, and 555 feet. Find the measure of the largest angle. (Round your answer to one decimal place.)

Solution

The largest angle is opposite to the side that measures 730 feet.
Using the Law of Cosines we now have
730^2= 655^2+ 555^2 -2(655)(555)cos (x)
where x is the largest angle
Cosx = [655^2+555^2 -730^2] / (2*655*555)
Cosx = 0.2807
x= cos^-1( .2807)
x= 73.7 degrees is our largest angle