The longitudinal displacement of sound wave

[Any Help]

Homework Statement

The longitudinal displacement of a mass element in a medium as a sound wave passes through it is given by s = sm cos (kx – ωt). Consider a sound wave of frequency 330 Hz and wavelength 0.95 m. If sm= 16 µm, what is the displacement of an element of air located at x = 1.1 m at time t = 0.12 s?

Homework Equations

k=2π/λ
ω=2πƒ
ƒ≡ frequency
ω≡ angular frequency
λ≡ wavelength
k≡ angular wave number

The Attempt at a Solution

substitute the values of λ and f in k and ω to get k=6.6138 m^-1 and ω=2073.45
∴ s= 16 cos ( 6.6138*1.1-2073.45*0.12)=-7.625 INCORRECT
Where I made mistake?

 

[TSny]

The argument of the cosine function is in what units? Radians or degrees?