Answer:
I believe the answer is A:
Step-by-step explanation:
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if x^2=40 you would need to square root both sides to get x alone therefore x=6.3
We know that
applying the law of cosines
c²=a²+b²-2*a*b*cos C
in this problem
a=10 m
b=11 m
c=13 m
C=?
c²=a²+b²-2*a*b*cos C----> cos C=[a²+b²-c²]/[2*a*b]
cos C=[10²+11²-13²]/[2*10*11]----> cos C=0.2364
C=arc cos (0.2364)----> C=76.33°
the answer is
76.3°