USING THE
PYTHAGOREAN THEOREM IN CONSTRUCTION
Often, when builders
want to lay the foundation for the corners of a building, one of the methods
they use is based on the Pythagorean Theorem (serious!). In the previous
pages we explored some special right triangles. One of them is the
3-4-5 triangle.
Builders use this special
triangle (or a multiple of it, say, 9-12-15) when they don't have a carpenter's square
(an instrument for constructing right angles) handy.
This is the process they
follow:
-
First, they peg a string
down where they want a specific wall to be.
-
Then, they measure (in
feet usually) a length of the string that is a multiple of three, say two
times three, and mark that off (so they would be marking off a section
that was six feet long). Call the marked endpoints points A and B,
where B is where the corner is to be built.
-
Where they want the corner
to be (point B) they attach another piece of string. If we are basing
this method on the Pythagorean Theorem and using the special 3-4-5 right
triangle, what do you think the length of the second side should be?
Why? (click here
for the answer).
-
Then, using the Pythagorean Theorem as their guide, they
attach a piece of string at point A that corresponds to what the length
of the hypotenuse of a right triangle of side lengths 6 and 8 feet respectively
would be. What do you think that length should be? (click here
for the answer). Why?
-
Lastly, they bring the ends of the second and third pieces
of strings together. Why do you think they do that?
-
Voila! We now have a right angle where we want the
corner to be courtesy of the Pythagorean Theorem!