Answer:
B
Step-by-step explanation:
You always have to use the Big Three trig functions (those that are on your calculator when answering this kind of question involving right angle triangles).
y is the adjacent side of the triangle. It is the side (other than the hypotenuse -- which is the longest side of the right triangle) that makes up the cosine.
Cos(45) = y / 4 sqrt(2)
Cos(45) = sqrt(2)/2
Multiply both sides by 4 sqrt(2)
4*sqrt(2) * cos(45) = y
4*sqrt(2) * sqrt(2)/2 = y
2*2 = y
y = 4
I can't tell you where all the other choices are coming from.
