Finding Displacement from Velocity

Time derivative of position function x(t)x(t) is velocity function v(t)v(t),

ddtx(t)=v(t),(1)\tag{1} \frac{d}{dt} x(t) = v(t),

and integral of velocity function v(t)v(t) with respect to time tt will give position function x(t)x(t),

x(t)=v(t)dt+C,(2)\tag{2} x(t) = \int v(t) dt + C,

with CC is constant of integration. If it becomes definite integral

x(t)x(t0)=t0tv(t)dt,(3)\tag{3} x(t) - x(t_0) = \int_{t_0}^t v(t) dt,

then the integration constant CC has the role as initial position x(t0)x(t_0).