C. 1/root2
Based on the information, the hypotenuse will be 6root2 because it is a 45, 45, 90 triangle. The two legs will be 6. Using SOH CAH TOA, we know that for cosine, it will be adjacent/hypotenuse. The adjacent side is 6 and the hypotenuse is 6root2. The result will be (6)/(6root2). After simplifying, we get
1/root2.
