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°
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°