ANSWER:
A diagonal fold which runs from the bottom-left corner to the top-right corner.
This would be the angle bisector of XAB as it would run directly through the centre of the angle, thus bisecting it.
I have attached an image which visually represents this. The blue lines are meant to be the angle XAB while the red line is the diagonal fold / angle bisector.
Hope this helps! <3
A diagonal fold which runs from the bottom-left corner to the top-right corner.
This would be the angle bisector of XAB as it would run directly through the centre of the angle, thus bisecting it.
I have attached an image which visually represents this. The blue lines are meant to be the angle XAB while the red line is the diagonal fold / angle bisector.
Hope this helps! <3