Answer
The amplitude of the resultant wave is $~~0.52~m$
Work Step by Step
We can find the amplitude of the resultant wave:
$y_m' = 2y_m~cos~\frac{\phi}{2}$
$y_m' = (2)(0.30~m)~cos~\frac{\pi/3}{2}$
$y_m' = (0.60~m)~cos~\frac{\pi}{6}$
$y_m' = 0.52~m$
The amplitude of the resultant wave is $~~0.52~m$
