Q:

A triangle has sides of length 11 m, 12 m, and 16 m.What is the measure of the angle opposite the side that is 16 m long? Round to the nearest degree.

Accepted Solution

A:
we know that
 the law of cosines formulas established 
c²=a²+b²-2*a*b*cos C-----> cos C=[a²+b²-c²]/[2*a*b]
a=11 m
b=12 m
c=16 m
so
cos C=[11²+12²-16²]/[2*11*12]---> cos C=0.0341
C=arc cos (0.0341)-------> C=88.05°

see the attached figure

the answer is
the angle is 88°