The image is two arcs in the first and third quadrants, which are symmetrical about the origin, do you know?

The minimum value is actually a line segment passing through the origin, which intersects with two arcs at (x 1, y 1)(x2, y2), x 1=y 1, x2=y2. You can make a circle with the origin as the center and the radius of 3, which is tangent to two arcs, and get (x 1, x2 = y2).