Help on output formatting

Question

Again, I am writing homework sheets. I have tried

 a = "(portionOfCircle)";
 SectorArea =  a * Pi * r^2 
 SectorArea =  a * Pi * r^2 // TeXForm
 With[{a = "portionOfCircle"}, Defer[a * Pi * r^2 // TeXForm]]

I would like the output to be in LaTeX form such as $$\text{(portion of circle)}\cdot \pi r^2$$ instead my code will output $$\pi \text{(portion of circle)}\cdot r^2$$

Also, I would like

 a = RandomChoice[{Pi/6, Pi/4, 5 Pi/4}]/(2 Pi)
 SectorArea = a*Pi*r^2
 SectorArea = a*Pi*r^2 // TeXForm
 With[{a = a}, Defer[a*Pi*r^2]]

to output $$\frac{\pi/4}{2\pi}\cdot \pi r^2$$ instead, it simplifies the fraction hiding the concept i'm trying to emphasize.

Any help would be much appreciated.

Answer 1

Just to clarify my comment earlier, here is a solution for the second part of the question (no need to duplicate an answer to the first part) that I think serves the intended purpose:

Row[{Row[{RandomChoice[{Pi/6, Pi/4, 5 Pi/4}]}]/HoldForm[2 Pi], 
   " \[Times] ", HoldForm[Pi*r^2]}] // TraditionalForm

Here I added the \[Times] symbol just to show that you can add arbitrary decorations by means of Row, to make the output look even clearer.

Answer 2

What you want to use (for the first part) is HoldForm.

i.e.

TeXForm@With[{a = "portionOfCircle"}, HoldForm[a*Pi*r^2]]

which returns

\text{portionOfCircle} \pi  r^2

as desired.

The problem with using Defer is that it simply holds until the expression evaluated. In your example, when the output of Defer is fed to TeXForm it gets evaluated prior to formatting it for TeX output. HoldForm will preserve the form under all future manipulations until you explicitly call ReleaseForm.