"That's how it's done"

• Math-proof letters
• Familiar inits. in math
• End of many an argument
• Triumphant end?
• Proof closer
• Letters after a proof
• Mathematician's letters
• Logical conclusion letters

Wikipedia Word definitions in Wikipedia
QED were an Australian New Wave trio, whose lead singer, Jenny Morris , went on to achieve commercial success as a solo artist. The band had a top twenty hit single, "Everywhere I Go", on the Australian Kent Music Report in 1983.

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
QED \Q.E.D\, QED \QED\(k[=u]"[=e]*d[=e]"), interj. [From Latin, quod erat demonstrandum, i.e. which was demonstrated.] Which was demonstrated; -- a phrase used after the conclusion of some line of reasoning, especially in mathematical or logical proofs. ...