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The golden spiral is a logarithmic spiral that grows outward by a factor of the golden ratio for every 90 degrees of rotation (pitch angle about 17.03239 degrees). It can be approximated by a "Fibonacci spiral", made of a sequence of quarter circles with radii proportional to Fibonacci numbers.
The result, though not a true logarithmic spiral, closely approximates a golden spiral. [2] Another approximation is a Fibonacci spiral, which is constructed slightly differently. A Fibonacci spiral starts with a rectangle partitioned into 2 squares. In each step, a square the length of the rectangle's longest side is added to the rectangle.
Both the Fibonacci sequence and the sequence of Lucas numbers can be used to generate approximate forms of the golden spiral (which is a special form of a logarithmic spiral) using quarter-circles with radii from these sequences, differing only slightly from the true golden logarithmic spiral. Fibonacci spiral is generally the term used for ...
A Fibonacci prime is a Fibonacci number that is prime. The first few are: [46] 2, 3, 5, 13, 89, 233, 1597, 28657, 514229, ... Fibonacci primes with thousands of digits have been found, but it is not known whether there are infinitely many. [47] F kn is divisible by F n, so, apart from F 4 = 3, any Fibonacci prime must have a prime index.
Logarithmic spiral (also known as equiangular spiral) 1638 [4] = Approximations of this are found in nature Fibonacci spiral: Circular arcs connecting the opposite corners of squares in the Fibonacci tiling Approximation of the golden spiral Golden spiral
The representation of the Fermat spiral in polar coordinates (r, φ) is given by the equation = for φ ≥ 0. The parameter is a scaling factor affecting the size of the spiral but not its shape. The two choices of sign give the two branches of the spiral, which meet smoothly at the origin.
A hyperbolic spiral is some times called reciproke spiral, because it is the image of an Archimedean spiral with a circle-inversion (see below). [ 6 ] The name logarithmic spiral is due to the equation φ = 1 k ⋅ ln r a {\displaystyle \varphi ={\tfrac {1}{k}}\cdot \ln {\tfrac {r}{a}}} .
The sequence also has a variety of relationships with the Fibonacci numbers, like the fact that adding any two Fibonacci numbers two terms apart in the Fibonacci sequence results in the Lucas number in between. [3] The first few Lucas numbers are 2, 1, 3, 4, 7, 11, 18, 29, 47, 76, 123, 199, 322, 521, 843, 1364, 2207, 3571, 5778, 9349, ... .