You are hundred percent correct, there were a few typos, it should have been 0.054m and also I did mix up the right hand side of the equation, it should have been vi/xi my apologies! I was running late and trying to get my post down quickly.
I have never seen that formula for max velocity. I'm...
position and velocity expressions for the initial conditions
1) x(0)=Acosφ = xi
2) v(0)=-ωAsinφ= vi
Dividing 2nd equation by equation results in:
-ωAsinφ/Acosφ = xi/vi
tanφ = xi/(-ωvi)
tanφ = 0.4
And here they (the textbook) got φ = 0.127π, This is where I...