| Take a right triangle with a square on its hypotenuse and rescale both of them by the same amount, as if on a photocopier. |
| The square of the length of the hypotenuse of a right triangle is equal to the sum of the squares of the legs. |
| In fact it is the length of the hypotenuse of a right angled triangle which had sides of length one. |
| With sides 1 and 4, a right-angled triangle has hypotenuse 10 and, although 10 is not a Fibonacci number it is twice a Fibonacci number. |
| The area of a right triangle is 150 square feet, and its hypotenuse is 25 feet. |
| Through that point draw a horizontal line to the intersection with the hypotenuse. |
