Answer:
BC = 50
Explanation:
Law of Cosines:
c^2 = a^2 + b^2 - 2ab*cosy (c is BC)
c^2 = 30^2 + 21^2 - 2(30)(21)cos123
c^2 = 900 + 441 - 1260*(-0.888)
c^2 = 1341 - (-1118.841)
c^2 = 2459.841
c = 49.597
c = 50
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