y(x,t)=Acos(ωt+βx+ϕ) in this equation ωt and βx symbols of the coefficient are same i.e( ++ or --) then the wave is negative direction travelling wave.

y(x,t)=Acos(ωt−βx+ϕ) in this equation ωt and βx symbols of the coefficient are alternative i.e( +- or -+) then the wave is positive direction travelling wave.

$y(x,t)=A\cos(\omega t+\beta x+\phi)$ in this equation $\omega t$ and $\beta x$ symbols of the coefficient are same i.e( ++ or --) then the wave is negative direction travelling wave.

$y(x,t)=A\cos(\omega t−\beta x+\phi)$ in this equation $\omega t$ and $\beta x$ symbols of the coefficient are alternative i.e( +- or -+) then the wave is positive direction travelling wave.