Mathematica Mathematical Logic - Dandah symbol for discharging assumptions ....

AI Thread Summary
The discussion revolves around the use of the 'dandah' symbol in mathematical logic as described in Ian Chiswell and Wilfred Hodges' book, specifically in Chapter 2 on Informal Natural Deduction. The term 'dandah' refers to a notation used to indicate that an assumption, represented by the symbol \phi, has been discharged. Participants in the thread provide guidance on how to represent this symbol in LaTeX. The recommended solution involves using the 'cancel' package, allowing users to denote a discharged assumption with the command \cancel{\phi}. It is noted that while MathJax automatically loads the cancel package, users must include it in their LaTeX documents using the \usepackage command. Additional methods for indicating discharged assumptions, such as enclosing them in square brackets or using numbering, are also mentioned.
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I am reading the book Mathematical Logic by Ian Chiswell and Wilfred Hodges (C&H) ... and am currently focused on Chapter 2: Informal Natural Deduction ...

I need help with what C&H call the 'dandah' or more specifically symbols with a dandah through them ...

The relevant text in C&H explaining and showing the use of the dandah is as follows (C&H page 17) ...
https://www.physicsforums.com/attachments/5002
In the above text we read the following:

" ... ... we discharge $$\phi$$ by writing a dandah through it ... ... "

My question is as follows:

Is there Latex code so that we can represent $$\phi$$ with a dandah through it as shown in the extract from C&H above ... can someone explain how such a symbol can be achieved in Latex?

Would be grateful for some help ... ...

Peter
 
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Peter said:
I am reading the book Mathematical Logic by Ian Chiswell and Wilfred Hodges (C&H) ... and am currently focused on Chapter 2: Informal Natural Deduction ...

I need help with what C&H call the 'dandah' or more specifically symbols with a dandah through them ...

The relevant text in C&H explaining and showing the use of the dandah is as follows (C&H page 17) ...

In the above text we read the following:

" ... ... we discharge $$\phi$$ by writing a dandah through it ... ... "

My question is as follows:

Is there Latex code so that we can represent $$\phi$$ with a dandah through it as shown in the extract from C&H above ... can someone explain how such a symbol can be achieved in Latex?

Would be grateful for some help ... ...

Peter

Hi Peter,

What you need for this is the >>cancel package<<. In the documentation you'll find how to do this and some other similar stuff as well.
 
Other authors show that an assumption is discharged by enclosing it in square brackets or by writing a number like (1) over it, which is then copied near the rule that discharges the assumption.
 
Sudharaka said:
Hi Peter,

What you need for this is the >>cancel package<<. In the documentation you'll find how to do this and some other similar stuff as well.
Thanks Sudharaka ... appreciate your help ...

So I should be able to show a discharges assumption by \cancel{ \phi }

as follows: $$\cancel{ \phi }$$

Thanks again,

Peter

- - - Updated - - -

Evgeny.Makarov said:
Other authors show that an assumption is discharged by enclosing it in square brackets or by writing a number like (1) over it, which is then copied near the rule that discharges the assumption.
Thanks for the further help, Evgeny ...

Peter
 
Peter said:
Thanks Sudharaka ... appreciate your help ...

So I should be able to show a discharges assumption by \cancel{ \phi }

as follows: $$\cancel{ \phi }$$

Thanks again,

Peter

Yes, MathJax seems to load the cancel package by default. In a document you'll have to load it in the beginning with the \usepackage command.
 
Sudharaka said:
Yes, MathJax seems to load the cancel package by default. In a document you'll have to load it in the beginning with the \usepackage command.

In our implementation of MathJax here at MHB, we autoload all of their available packages. :D
 

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