We are given an equation which describes a wave on a string:
D(x,t) = 3.6cm * sin[2π (x/4.8m) + t/(0.14s) + 1)]
where x is in meters
t is in seconds
at t = 0.42 seconds, and x = 5.2 m
First, convert the term into the equation with cm units:
D(x,t) = 3.6cm/100cm/m * sin[2π (x/4.8m) + t/(0.14s) + 1)]
then, substitute the values of x and t
D(x,t) = 3.6cm/100cm/m * sin[2π (5.2/4.8m) + 0.42/(0.14s) + 1)]
Solve for D, this is your displacement at x = 5.2 and at 0.42 seconds
