In triangle ABCABCABC, a=5a = 5a=5, b=6b = 6b=6, c=7c = 7c=7. Find sin(A)\sin(A)sin(A) using the Law of Cosines first.
sin(A)=1114\sin(A) = \frac{\sqrt{11}}{14}sin(A)=1411
sin(A)=61135\sin(A) = \frac{6\sqrt{11}}{35}sin(A)=35611
sin(A)=1235\sin(A) = \frac{12}{35}sin(A)=3512
sin(A)=514\sin(A) = \frac{5}{14}sin(A)=145