The sides of a triangle measure 18 inches, 25 inches, and \(38\) inches. To the nearest degree, what is the measure of the largest angle?
The greatest angle is opposite the longest side
Using the Law of Cosines and doing some rearranging, we have
[ 38^2 - 25^2 - 18^2 ] / [ -2 (18)(25) ] cos (theta )
arccos ( [ 38^2 - 25^2 - 18^2 ] / [ -2 (18)(25) ] ) = theta ≈ 123.4°
