I understand how to solve this problem ,however cannot figure out why the .5 degrees is being converted to radians:

Question

PROBLEM:

How would one determine the percent uncertainty in theta and in sin of theta for the following:

1) theta = 15.0 degrees +/- 0.5 degrees

SOLUTION:

f(θ) = sin(θ)
f'(θ) = cos(θ)
For θ = 15°
d(cos(θ))
= ±cos(θ) dθ
= ±cos(15°) (0.5°)
= ±0.9659*(0.5*π/180) <---- Why is .5 degrees converted to radians?
= ±0.00843