the direction in which a parametric curve is generated as the parameter increases is called the positive orientation of the curve (and is indicated by arrows on the curve)

Parametric Equation of a Line

The equation
and for the line is vertical

Derivative for the Parametric Curves

Let and where f and g are differentiable on an interval [a,b]. then the slope of the line tangent to the curve at the point corresponding to t is
provided