math formatting: "cancelling"?

[stapel]

Is there a way to show cancellation, as in fractions, in LaTeX?

Thank you.

Eliz.

 

[opticaltempest]

Using TeXAide,

\(\displaystyle \frac{{\rlap{--} 1}}{{\rlap{--} 2}}\)

\rlap is supposed to cause the text to be strikethrough but it appears not
to work on the forum


\(\displaystyle \frac{{\not 1}}{{\not 2}}\)

Ok \not appears to work. But you can only "not" out individual characters.

 

[Gene]

Stealing from Soroban

\(\displaystyle \L2x(\not{x-1})\left(\frac{x}{\not{x-1}}\right)\,-\,2\not{x}(x-1)\left(\frac{3}{\not{x}}\right)\:=\:\not{2}x(x-1)\left(\frac{1}{\not{2}}\right)\)

Removing the tex boxes he typed

\L2x(\not{x-1})\left(\frac{x}{\not{x-1}}\right)\,-\,2\not{x}(x-1)\left(\frac{3}{\not{x}}\right)\:=\:\not{2}x(x-1)\left(\frac{1}{\not{2}}\right)

----------------------
Gene

 

[stapel]

The single-character limitation could be a problem, I think. Is there no way to cancel out an entire term? So, for instance, in what follows, we could illustrate the cancelling of the entire "x + 1" factor, rather than appearing to cancel out only the "plus" sign in the middle?

. . . . .\(\displaystyle \large{\frac{\not{(x\,+\,1)}}{(x\,-\,1)\not{(x\,+\,1)}}\,=\,\frac{1}{x\,-\,1}}\)

I tried the "cancel" command, but the LaTeX installed here doesn't appear to understand it.

Eliz.

 

[tkhunny]

Why not just regroup it and skip the odd concept of "cancelling".

P.S. I know, I'm out on the edge of my Ivory Tower again.

 

[stapel]

Why not just regroup it....

True, true... but some students still seem to miss what's going on, and showing the "cancellation" can help sometimes.


Not always, though....


I had a friend who was doing his shift in the Math Help Room one day. A student was having trouble simplifying something along the lines of:


. . . . .\(\displaystyle \large{\frac{3\sin{(\theta)}}{3\cos{(\theta)}}}\)


My friend suggested that the student simplify, so the student did:


. . . . .\(\displaystyle \large{\frac{\not{3}\sin{(\theta)}}{\not{3}\cos{(\theta)}}\,=\,\frac{\sin{(\theta)}}{\cos{(\theta)}}}\)


When my friend suggested that the student could simplify further, the student blinked a couple times, and then did:


. . . . .\(\displaystyle \large{\frac{\not{s}\mbox{in}\not{(\theta)}}{\mbox{co}\not{s}\not{(\theta)}}\,=\,\frac{\mbox{in}}{\mbox{co}}}\)

Oy. :roll:

Eliz.

 

[galactus]

Is this what you want?. Use \sout{}

\(\displaystyle \sout{strikethrough}\)

\(\displaystyle \frac{sinx}{\sout{cosx}}\frac{\sout{cosx}}{tanx}\)

\(\displaystyle \frac{\sout{(x+1)}}{(x-1)\sout{(x+1)}}\)

 

[stapel]

Let's see....


. . . . .\(\displaystyle \large{\frac{(x\,+\,1)}{(x\,-\,1)(x\,+\,1)}\,=\,\frac{\sout{(x\,+\,1)}}{(x\,-\,1)\sout{(x\,+\,1)}}\,=\,\frac{1}{x\,-\,1}}\)


That'll work!

Excellent! Thank you!

Eliz.