If the bottom is a right triangle, then the circumscribed circle of the bottom is at the midpoint of the hypotenuse, and the circumscribed spherical center must be on a straight line perpendicular to the bottom with the midpoint of the hypotenuse as the vertical center.

The bottom is a regular triangle, so the center of the circumscribed circle of the bottom is at the center of the regular triangle, so the center of the circumscribed ball must be on a straight line perpendicular to the bottom with the center of the bottom as the vertical center.