A 1 kg mass is attached to a spring with constant k = 16 N/m. Find the motion x(t) in amplitude-phase form (2.37) if x(0) = 1 and x′(0) = −1.
Ignore damping forces.
combined with 3
The Attempt at a Solution
So I know m=1, k=16, c=0, x0=1, and v0=-1
x(t)=c1*cos(4t)+c2*sin(4t) (e^0t = 1 and is excluded)
initially x0=1 so
use intial value of -1 for v
tan(phi)=c2/c1=-.245, add pi =2.90
so now we have
the book says the answer should be sqrt(17)/16*cos(4t-6.038)
so I all have right is the angular frequency
where did I mess up?