\pgfmathparse{1} \let\r\pgfmathresult;


\pgfmathparse{0.75} \let\dx\pgfmathresult;
\pgfmathparse{1.5} \let\dy\pgfmathresult;
\pgfmathparse{3} \let\k\pgfmathresult;

%Convex parameters for drawing lines
\pgfmathparse{1.2} \let\t\pgfmathresult;
\pgfmathparse{-0.35} \let\tt\pgfmathresult;

\coordinate (V) at (4.5,0);

%Define nodes
\coordinate (A1) at ( 0,0);
\coordinate (A2) at ($(A1)+    (\dx,0)$);
\coordinate (Ak) at ($(A1)+ \k*(\dx,0)$);

\coordinate (P) at (0.5,1);
\coordinate (S) at (2.5,1);
