\begin{tikzpicture}\coordinate (T) at (0,0);
            \coordinate (zo) at (.5,-1);
            \coordinate (p1) at (2.1,1.4);
            \coordinate (p2) at (3,1.5);
            \coordinate (z) at (.9,-.4);
            \tkzMarkRightAngle[fill=lightgray](zo,z,T)
            \draw (T)--(zo);
            \draw[->] (zo)--(p1) node[above]{(1)};
            \draw[<->](-1,-.5)--(p2) node[right]{(4)};
            \draw[<->](-.9,.4)--(2.7,-1.2) node[right]{(2)};
            \tkzDrawCircle[color=blue](zo,T)
            \draw (-.6,-1.9) node{\(C\)};
            \draw (.1,-.7) node{(3)};
            \tkzLabelPoint[above](T){\(t\)};
            \tkzLabelPoint[below](zo){\(z_0\)};
            \tkzLabelPoint[below](z){\(z\)};
            \tkzInterLL(zo,z)(T,p2)\tkzGetPoint{zstar}
            \tkzMarkRightAngle[fill=lightgray](zo,T,zstar)
            \tkzDrawPoints(T,zo)
            \tkzDrawPoints[fill=red](zstar,z)
            \tkzLabelPoint[right](zstar){\(z^*\)};
            \draw (.5,-3) node{(a)};
  
          \begin{scope}[xshift=5cm]
          \coordinate (zo) at (.5,-1);
          \coordinate (r) at (0,0);
          \tkzDrawCircle[color=blue](zo,r)
          \draw (-.6,-1.9) node{\(C\)};
          \coordinate (z) at (2.3,.2);
          \tkzDefMidPoint(zo,z)\tkzGetPoint{m}
          \tkzLabelPoint[left](zo){\(z_0\)};
          \tkzLabelPoint[right](z){\(z\)};
          \tkzDrawCircle(m,zo)
          \draw(1.5,0.9) node{(1)};
          \tkzInterCC(zo,r)(m,zo)\tkzGetPoints{T}{T1}
          \tkzLabelPoint[above](T){\(t\)}
          \tkzDefLine[perpendicular=through T,
          K=.-1](zo,z)
          \tkzGetPoint{c}
          \tkzDefPointBy[projection=onto zo--z](c)
          \tkzGetPoint{zstar}
          \tkzMarkRightAngle[fill=lightgray](zo,zstar,T)
          \tkzDrawLines[](zo,z T,c)
          \tkzDrawPoints(zo,T)
          \tkzDrawPoints[fill=red](z,zstar)
          \draw (2.2,-2) node{(2)};
          \tkzLabelPoint[right](zstar){\(z^*\)}
          \draw (.5,-3) node{(b)};
          \end{scope}
            \end{tikzpicture}