Q.E.D.

Q.E.D. is an abbreviation for the Latin phrase quod erat demonstrandum meaning "which was to be demonstrated." Q.E.D. may appear at the conclusion of a text to signify that the author's overall argument has just been proven.

See, e.g. Stupak-Thrall v. U.S., 89 F.3d 1269, 1299 (6th Cir. 1996) - “Riparian rights are not mineral rights and therefore should not be protected from Forest Service regulation. Quod erat demonstrandum.”