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Wave equations of two particles are given by ${y}_{1}=a\mathrm{sin}(\omega \text{\hspace{0.17em}}t-kx)$, ${y}_{2}=a\mathrm{sin}(kx+\omega \text{\hspace{0.17em}}t)$, then

(1) They are moving in opposite direction

(2) Phase between them is 90°

(3) Phase between them is 180°

(4) Phase between them is 0°