An equation with third parametric are called Parametric equations . In this type of equation two variable defines in terms of third variable to form two equation. Third common variable is know as parameter. Due to parameter these equation call parametric equation. Likewise x = f(t) and y = g(t), where t is parameter. Also we can say x and y  do not give the relationship between x and y directly in the form y = f(x).

 

Parametric Equations

Parametric Eq.