Answer
$y_m=0.45\;cm$
Work Step by Step
The equation for one of the two waves be of the form: $y(x, t)=y_m\sin(kx+\omega t)$
The other wave has the same amplitude and wavelength and travel through each other.
From the given graph,
$2y_m=\frac{H}{2}$
or, $y_m=\frac{H}{4}$
or, $y_m=\frac{1.80}{4}\;cm$
or, $\boxed{y_m=0.45\;cm}$
