Page 387 - HOW TO PROVE IT: A Structured Approach, Second Edition

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Appendix 2

Proof Designer

Proof Designer is a Java applet that writes outlines of proofs in elementary set
theory, under the guidance of the user. It should work on any computer with
a sufficiently up-to-date version of Java, including both PC and Macintosh
computers. To use Proof Designer, open your web browser and go to the Proof
Designer website:
http : //www.cs.amherst.edu/~djv/pd/pd.html

Complete instructions for using Proof Designer can be found at the website.
Here we will provide an outline of these instructions.
When you open the Proof Designer home page in your browser you should
see a button at the bottom of the page that says “Write a Proof.” (If you don’t,
you may need to follow the instructions at the website for setting up your
computer to use Proof Designer.) To start writing a proof, click on the Write a
Proof button.
A dialog box will open, asking you to enter the hypotheses and conclusion
of the theorem you want to prove. The hypotheses and conclusion are entered
1
using ordinary set-theoretic and logical notation. When you have entered the
hypotheses and conclusion, click OK.
The dialog box will close, and a new window will open. The window will
contain three menus, called “Edit,” “Strategy,” and “Infer.” Below the menus
will be the statement of the theorem you are proving, and then a place where

1
There is one significant difference between the way set theory notation is used in Proof Designer
and the way we have used it in this book. The difference concerns intersections of families of
sets. In this book, we have used the notation ∩F only in contexts in which we could be sure that
F = ∅; the reason for this rule is discussed in exercise 14 of Section 2.3. Proof Designer enforces
this rule by restricting the contexts in which the notation ∩F can be used. For further details
about this, and a more complete explanation of how to type statements into Proof Designer, see
the website.
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