Respuesta :

It's C the missing side is 9 units long so since cosine is adjacent divided by hypotenuse it would be 9/41
41^2 - 40^2 = 1681 - 1600 = 81

side xy = square root 81 = 9

cosine(X) = Adj / Hypo
cosine(X) = 9/41
answer
C. 9/41