\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}