Since the one angle is 45 degrees, and it is a right triangle, the other angle is also 45 degrees. This means that the base of the triangle is also 3.
Now, we can use the Pythagorean Theorem.
a^2 + b^2 = c^2
3^2 +3^2 = c^2
9+9=c^2
18=c^2
c=sqrt(18)
Therefore, the hypotenuse of the triangle is the square root of 18.