Problem
In $\triangle \mathrm{MNO}, m=89$ inches, $n=30$ inches and $o=71$ inches. Find the measure of $\angle \mathrm{M}$ to the nearest degree.
Solution
Step 1 ：Using the Law of Cosines: \(89^2 = 30^2 + 71^2 - 2(30)(71)\cos(M)\)
Step 2 ：Solving for M: \(\boxed{118}\) degrees
