Get a slanting crease on the paper. Now, try to get another crease that is perpendicular to the slanting crease. a. How many right angles do you have now? Justify why the angles are exact right angles. b. Describe how you folded the paper so that any other person who doesn't know the process can simply follow your description to get the right angle.
Four right angles are formed at the intersection of the two perpendicular creases. The angles are exact right angles because the folding process ensures the crease divides the straight angle into two equal parts, each measuring 90°.
First, create a slanting crease by folding the paper at any angle. Then, fold the paper again so that the slanting crease line overlaps onto itself perfectly. The new crease formed will be perpendicular to the first crease, creating right angles.
Explanation
(a) When two perpendicular lines intersect, they form four right angles. The folding method creates perpendicular lines because the crease bisects the straight angle. (b) This method works because when a line is folded onto itself, the crease created is perpendicular to that line, bisecting it at a right angle.