Derivative of Parametric Functions

Key Questions

  • Let {(x=x(t)),(y=y(t)):}.

    First Derivative

    {dy}/{dx}={{dy}/{dt}}/{{dx}/{dt}}={y'(t)}/{x'(t)}

    Second Derivative

    {d^2y}/{dx^2}=d/{dx}[{y'(t)}/{x'(t)}]=1/{{dx}/{dt}}{d}/{dt}[{y'(t)}/{x'(t)}]

    by Quotient Rule,

    =1/{x'(t)}cdot{y''(t)x'(t)-y'(t)x''(t)}/{[x'(t)]^2}

    ={y''(t)x'(t)-y'(t)x''(t)}/{[x'(t)]^3}

    I hope that this was helpful.

  • To find the derivative of a parametric function, you use the formula:

    dy/dx = (dy/dt)/(dx/dt), which is a rearranged form of the chain rule.

    To use this, we must first derive y and x separately, then place the result of dy/dt over dx/dt.


    y=t^2 + 2

    dy/dt = 2t (Power Rule)


    x=tsin(t)

    dx/dt = sin(t) + tcos(t) (Product Rule)


    Placing these into our formula for the derivative of parametric equations, we have:

    dy/dx = (dy/dt)/(dx/dt) = (2t)/(sin(t)+tcos(t))

  • For the parametric equations

    {(x=x(t)),(y=y(t)):},

    we can find the derivative

    {dy}/{dx}={{dy}/{dt}}/{{dx}/{dt}}={y'(t)}/{x'(t)}.

Questions