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Homework Statement
The figure shows the displacement y versus time t of the point on a string at x = 0, as a wave passes through that point. The scale of the x axis is set by ys = 84.0 mm.The wave has form y(x, t) = ym sin (kx  ωt+φ). What is φ? (Caution: A calculator does not always give the proper inverse trig function, so check your answer by substituting it and an assumed value of ω into y(x, t) and then plotting the function.)
Homework Equations
y(x, t) = ym sin (kx  ωt+φ)
The Attempt at a Solution
This is supposed to be really easy but the solution I got was wrong. My approach was straight forward:
read off the initial y value  y(0,0)=0.028
and sub in the equation: 0.028=0.084sin(00+φ)
φ=arcsin(0.028/0.084)=0.339836.......=0.340 rad
The question mentioned that the calculator might give the wrong value but I do not see how I could make amend to it.
Please enlighten me!
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