set of points called primary points~\cite{idrees2014coverage}. We assume that
the sensing disk defined by a sensor is covered if all the primary points of
this sensor are covered. By knowing the position of wireless sensor node
-(centered at the the position $\left(p_x,p_y\right)$) and it's sensing range
+(centered at the the position $\left(p_x,p_y\right)$) and its sensing range
$R_s$, we define up to 25 primary points $X_1$ to $X_{25}$ as decribed on
Figure~\ref{fig1}. The optimal number of primary points is investigated in
section~\ref{ch4:sec:04:06}.
