Why isn't the graph of the equation a line and a circle?

Questions
1

2025-09-11_163033.png

ContourPlot[
 Evaluate@(x - 2) Sqrt[x^2 + y^2 - 5] == 0, {x, -3, 3}, {y, -3, 3}, 
 Frame -> False, Axes -> True, AspectRatio -> Automatic]

2025-09-11_163422.png
2025-09-11_163422.png662×642 5.16 KB

2

The circle is exactly the edge of the function domain. I suppose that the numeric algorithms of ContourPlot work mainly on sign variations, which do not happen across the circle. We must force some symbolic processing:

Region@ImplicitRegion[
  Reduce[(x - 2) Sqrt[x^2 + y^2 - 5] == 0, {x, y}, Reals],
  {{x, -3, 3}, {y, -3, 3}}]