I am typing up solutions to a variety of problems in a textbook, and I want to use the proof environment for proofs but a similar environment for solutions. The link here

Duplicating the amsthm proof environment

shows how I can make my own solution environment, but I want the indication for the end of a solution to be slightly different than that of a proof. I'd like solutions to end with the QED as \blackbox whereas I want the proof environment to stay as it is (white box to indicate QED). Is there an easy way to make this happen?

2 Answers 2


You also can do that very simply with ntheorem. Its advantage is an automatic placement of endmarks even if the environment ends in a display math environment:


\usepackage[thmmarks, amsmath, thref]{ntheorem}

\theoremseparator{. ---}
\newtheorem{varsol}{Solution (variant)}


    \begin{proof}Since something is true, we have
      \[ A = B. \]

    \begin{solution}[of some exercise]
      This is a very intricate solution.
        a & = b \\ c & = d.

      This solution is so very simple that it’s not even worth writing it. Just pure thought:

enter image description here

  • the black box to delineate end of exercise is not present. Commented Sep 21, 2020 at 0:16

Gonzalo's answer can be easily modified to do this. Just add \renewcommand\qedsymbol{$\blacksquare$} to the definition








enter image description here

  • What are the dimensions of the regular QED symbol? I'd like my black square to look exactly like that--I know you have 3mm and it looks like 2.5mm fits better, but I'm not sure of the exact size. Commented Nov 8, 2014 at 12:48

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