If the sin 30 degrees is 1/2, then the cos

Sin 30 degrees = 1 / 2 = opposite / hypotenuse

Adjacent^2 = hyp^2 - opp^2

Adj^2 = 4 - 1

Adj^2 = 3

Adj = sq root (3)

cosine 30 degrees = adjacent / hypotenuse

cosine 30 degrees = sq root (3) / 2

cosine 30 degrees = 1.732 / 2

cosine 30 degrees =.866