The Pythagorean Theorem In A Roof

The pythagorean theorem describes how the three sides of a right triangle are related in euclidean geometry.

The pythagorean theorem in a roof.

Since the roof forms an isosceles triangle the perpendicular from the top of the roof must divide the across length in two equal halves. The greeks 1500 years ago used full scale drawings of the roofs to develop the rafter lengths and bevels and used the pythagorean theorem to square up the strings they used for the geometric layout of the roof. Let the length of one side of the roof be x ft. In mathematics the pythagorean theorem also known as pythagoras s theorem is a fundamental relation in euclidean geometry among the three sides of a right triangle.

This theorem is talking about the area of the squares that are built on each side of the right triangle. You can also think of this theorem as the hypotenuse formula. By construction c lies on the circle with center a and radius b. The pythagorean theorem is just a special case of another deeper theorem from trigonometry called the law of cosines c 2 a 2 b 2 2 a b cos c where c is the angle opposite to the long side c.

Define points d and e on ab so that ad ae b. The triangles are similar with area 1 2 a b frac 1 2 ab 2 1 a b while the small square has side b a b a b a and area b a 2 b. What is the pythagorean theorem. The square on the hypotenuse of a right triangle is equal to the sum of the squares on the two legs eves 80 81.

As usual ab c ac b bc a. The roof pitch is the slope of the rafter. When c pi 2 or 90 degrees if you insist cos 90 0 and the term containing the cosine vanishes. It states that the area of the square whose side is the hypotenuse the side opposite the right angle is equal to the sum of the areas of the squares on the other two sides.

Proof 39 by j. The pitch is commonly defined as the ratio of rise over run in the form of x 12. The rise is the height of the roof and the run is the horizontal span as pictured above. The pythagorean theorem says that in a right triangle the square of a which is a a and is written a 2 plus the square of b b 2 is equal to the square of c c 2.

It states that the sum of the squares of the sides of a right triangle equals the square of the hypotenuse. Barry sutton the math gazette v 86 n 505 march 2002 p72 let in abc angle c 90 o. Pythagorean formula c 2 a 2 b 2 where a b are the legs of a right triangle and c is the hypotenuse. The pythagorean theorem is proven after two triangles are removed from each of the hexagons.

A 2 b 2 c 2 proof of the pythagorean theorem using algebra.