Ask the students to describe the shape. (E.g., the square has 4 sides. They are of equal length.)
Observe that the opposite sides are parallel. They do not meet.
The adjacent sides are perpendicular. They meet at a point. They meet at right angles.
STEP 2: FOLD THE PAPER IN HALF (HORIZONTALLY)
A new line segment is found.
This new line is perpendicular to two of the sides. It meets them at a point each, at right angles.
Now, there are three line-segments parallel to each other.
STEP 3: FOLD THE PAPER IN HALF (VERTICALLY)
This new line is perpendicular to the previous line.
It also intersects the previous line. These two lines are called intersecting lines. The point where they intersect is called the point of intersection.
Which are the parallel lines here?
How many pairs of perpendicular lines can you identify?
STEP 4: FOLD ALONG ONE DIAGONAL
This line is neither parallel nor perpendicular to any of the previous, existing lines.
It meets the lines from Fold (2) and (3) at the midpoint i.e., it intersects them.
These lines are intersecting lines.
STEP 5: FOLD ALONG THE OTHER DIAGONAL
Is the new line perpendicular to any of the previous lines?