Question 930849
find the angle of a triangle with sides of 10,15,20

find angle of A:

find angle of B:

find angle of C:
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Pick an angle and use the Cosine Law:
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20^2 = 10^2 + 15^2 - 2*10*15*cos(C)
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Then use the Law of Sines for the 2nd angle
sin(A)/a = sin(B)/b = sin(C)/c