Question 438018: In non-right triangle ABC, let A=120 degrees, a = 7cm, and b=3cm. Find side c and angles B and C.
I'm really not sure about this problem- I THINK I found angle B by- sinB/3=sin120/7. By cross multiplying I got sinB= 3sin120/7=.37
I then did sin^-1.37=21.72 degrees.
180-21.72=158.28 (degees as angle B). But i'm not quite sure if you could help with the rest i'd really appreciate it!
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! In non-right triangle ABC, let A=120 degrees, a = 7cm, and b=3cm.
Find side c and angles B and C.
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Use the Law of Sines:
sin(B)/b = sin(A)/a
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sin(B) = (b/a)sin(A)
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sin(B) = (3/7)sin(120) = 0.3712
B = sin^-1(0.3712) = 21.79 degrees
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So C = 180-[21.79+120] = 38.21 degrees
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c/sin(C) = a/sin(A)
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c = sin(C)[a/sin(A)
c = sin(38.21)[7/sin(120)]
c = 5
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Cheers,
Stan H.
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