You actually can do this

You actually can do this right now, although it's a little hidden. If you go to the Settings application, you can go into the Pi Cubed application settings. Tap on the "Copy equations as" item and select "Image".

Now, when you go to Pi Cubed, you can double-tap on the equation to bring up the Copy option, which will let you copy the equation onto the clipboard as an image. You can then paste the image into any application that supports images, such as Mail.

Additionally, it's pretty easy to mail yourself a PDF (which is black text on a transparent background) and export that to an image using something like the Mac's Preview application.

Sunset Lake Software - Comments for "Export equation as image"

You actually can do this