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

[Math Amateur]

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 \(\displaystyle \phi\) by writing a dandah through it ... ... "

My question is as follows:

Is there Latex code so that we can represent \(\displaystyle \phi\) 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

 

[Sudharaka]

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 \(\displaystyle \phi\) by writing a dandah through it ... ... "

My question is as follows:

Is there Latex code so that we can represent \(\displaystyle \phi\) 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.

 

[Evgeny.Makarov]

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.

 

[Math Amateur]

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: \(\displaystyle \cancel{ \phi }\)

Thanks again,

Peter

- - - Updated - - -

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

 

[Sudharaka]

Thanks Sudharaka ... appreciate your help ...

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

as follows: \(\displaystyle \cancel{ \phi }\)

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.

 

[MarkFL]

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