Well, the ladder against the wall creates a right triangle. We can use right triangle trig to find the length of the ladder. The length of the ladder represents the hypotenuse of the triangle. Because we know theta and the the distance from the wall to the foot of the ladder...
cos(60º) × hypotenuse = 4.6
0.5 × hypotenuse = 4.6
hypotenuse = 9.2 meters
answer: 9.2 meters