Four independent waves are expressed as
\[
(i)\; y_1=A_1\sin\omega t,
\]
\[
(ii)\; y_2=A_2\sin 2\omega t,
\]
\[
(iii)\; y_3=A_3\cos\omega t,
\]
\[
(iv)\; y_4=A_4\sin\left(\omega t+\frac{\pi}{3}\right)
\]
The interference between two of these waves is possible in