# UnMessUpable Perpendicular Lines

- Author:
- visualgeom

In the dynamic world of construction, we view good constructions as UnMessUpable.
Below you are given two examples of perpendicular lines. But only one of them is UnMessUpable. Which one? (To check, please move the pink points.)
Now it is your turn to construct an UnMessUpable pair of perpendicular lines. Your tools are limited, so please follow these steps:
(i) Click on the "Circle with Center through Point" tool. Construct circle EF, where point E is the center of the circle and the circle goes through point F.(ii) Construct circle FE, where point F is the center of the circle and the circle goes through point E.
(iii) Click on the "Intersection Two Objects" tool. Click on both circles where they intersect. A point will be placed at the point of intersection. To get a point at the other place of intersection, you will need to click on the other point of intersection.
(iv) Click on the "Line through Two Points" tool. Construct a line by clicking on the two points of intersection created by the two circles.
Congratulations, you should have constructed a pair of UnMessUpable perpendicular lines. But lets check to make sure ...
To check your work:
(1) With the "Arrow" tool activated, move points E and F in your construction to make sure the lines remain perpendicular.
(2) Click on the button called "Check" to see if your construction matches.