1. The problem statement, all variables and given/known data The position of a mass that is oscillating on a Slinky (which acts as a simple harmonic oscillator) is given by 18.5 cm cos[ 18.0 s-1t]. What is the speed of the mass when t = 0.360 s? 2. Relevant equations x(t)=Acos(ωt+θ) v(t)=-Aωsin(ωt+θ) 3. The attempt at a solution I used the formula, v(t)=-Aωsin(ωt+θ) because you basically have everything you need such as: A=18.5cm ω=18.0s^-1 t=0.360s What I get is: v(0.360)=-(18.5cm)(18.0)sin(18.0*0.360) to get -65.1cm/s which isn't the right answer. Please tell me where I went wrong!