You can use GeoGebra to study the power of a point theorem. 
     GeoGebra Instruction 1
Algebra     View     and         Graphics     View     under         View     in         Menu.         Circle     through 3     Points Circle     with     Center     through     Point Line Point     on     Object Point right-click     on                and         click         on         Rename.         Type                in         the         field         and         click         OK.         Line Intersect Segment Line right-click     on         Lines,         Segments     and         Circle     respectively         and         click         on         Show     Label     so         that         the         check         mark         disappears.