Gives
x=Acos(wt+ϕ)→(1)
A=amplitude
Phase=ϕ
Angular frequency=w
equation (1) differencuate with respect time
Velocity
v=Awsin(wt+ϕ)
t=0
v=Awsinϕ→(2)
t=2T
v=Awsin(T2π×2T+ϕ)
v=Awsin(π+ϕ)
v=Awsinϕ→(2)
equation (2)and(3)are same

Point P wave equation
t=2T Velocity of object
v=Asinϕ