Hello from MrBillDoesMath!
Answer:
12 sqrt(2)
Discussion:
Since we have a right triangle,
cos(45) = side adjacent/ hypotenuse
= 12/ c
As cos(45) = sqrt(2)/2 the above equation becomes
sqrt(2)/2 = 12/c => multiple each side by "c"
c sqrt(2)/2 = 12/c * c =>
c sqrt(2)/2 = 12 => divide both sides by sqrt(2)/2
c = 12/ (sqrt(2)/2) =>
c = 12 *2 / sqrt(2) => as 2/sqrt(2) = sqrt(2)
c = 12 sqrt(2)
which is the first answer provided.
Thank you,
MrB