$y_{1}=5 \sin 2 \pi(x-v t) \,c m\,$
$y_{2}=3 \sin 2 \pi(x-v t+1.5) \,c m$
These waves are simultaneously passing through a string. The amplitude of the resulting wave is.........$cm$
$y = a\sin (kx + \omega t)$ ......$(1)$
$y = a\sin (\omega t - kx)$ ......$(2)$
$y = a\cos (kx + \omega t)$ ......$(3)$
$y = a\cos (\omega t - kx)$ ......$(4)$
emitted by four different sources ${S_1},\,{S_2},\,{S_3}$ and ${S_4}$ respectively, interference phenomena would be observed in space under appropriate conditions when