Equation of the wave: y=Asin(kx−ωt+Φ) Here,A is the amplitude, k is the wave number, ω is the angular frequency and Φ is the initial phase.The argument of the sine is a phase, so the smallest positive phase constant should besin(7.5π)​=sin(3×2π+1.5π)=sin(1.5π)​ Therefore, the smallest positive phase constant is 1.5π.