You can put this solution on YOUR website! In the right triangle ABC(C= 90 deg.) a and c are labeled. Cos B = .4 and a=3 find c (hypot.)?
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arc cos (0.4) = 66.42 degrees
Sin 66.42 = 3/hyp
hyp = 3/sin66.42 = 3.2732
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Cheers,
Stan H.