The arc length formula is given below.
Arc Length, s = radius*theta where theta is in radians. First we need to convert theta from degrees to radians.
theta (radians) = 45 degrees * π radians / 180 degrees = 0.785 radians
radius = 6 ft
theta = 0.785 radians
s = arc length = 6 ft * 0.785 radians = 4.712 ft