Take a plain square sheet of paper and perform the following steps:
Fold the sheet horizontally in half to create a central horizontal crease line, \(l\).
Fold the sheet in half horizontally once more in the same direction, then unfold the paper completely.
Tasks:
(a) Calculate and state the total number of horizontal parallel lines (creases and edges) you can observe on the sheet now
(b) If you now make a completely new vertical fold straight down the middle of the sheet, what geometric relationship does this new vertical crease share with all your previous horizontal creases? Support your answer using the degree measure of the angle formed at their intersection.
Solution:
The new vertical crease shares a relationship (written as \(\text{vertical crease} \perp \text{horizontal creases}\)) with all your previous horizontal creases.
This is justified because the angle formed at every single intersection point is exactly a .