Calculating Phase Angle and Amplitude for a Sinusoidal Wave on a String

[armolinasf]

Homework Statement

At time t = 0 and at position x = 0 m along a string, a rightward (+x dir) traveling sinusoidal wave with frequency of 230 Hz has displacement y = +4.8 mm and transverse velocity vy = -0.75 m/s.

What is the smallest positive phase angle?

What is the amplitude of the wave?

How long does an observer at x=0 need to wait before a trough (y=-A) arrives?

The Attempt at a Solution

.0048=Asin(phi)
-.75=acos(phi)

arctan[2(pi)(230)(.0048/-.75)]=phi=-1.463

pi-1.463=1.678rad

For some reason this answer is incorrect and I don't know why since I used in my calculation of part B which is correct.

B) .0048/sin(1.678)=.00483m

Not sure how to approach part c...

As always thanks for the help

 

[armolinasf]

for c I would just solve t for -A correct, omega would be negative since the wave is moving rightward?

arcsin(-1)/(-2pi*230)=t=.0011

Does this make sense?