Let three points be (x 1, y 1, z 1), (x2, y2, z2), (x3, y3, z3), then the determined plane is as shown in the figure.

Namely:

(x-x 1)(y2-y 1)(z3-z 1)+(y-y 1)(z2-z 1)(x3-x 1)(x2-x 1)(y3-y 1)-(z-z 1)(y2-y 1)(y