A practical way of representing circular arcs with standard-form cubic rational Bézier curves containing a parameter is presented. The parameter affecting the control points

weights and shoulder points is discussed. The inner relation between the parameter and the weights of representing circular arcs with nonstandard-form quadratic rational Bézier curves is analyzed in detail. Modifing the parameter value corresponds to a rational linear parameter transformation. Finally

we discuss the inverse calculation of the standard-form cubic rational Bézier representation of circular arcs.