The mathematician Fibonacci or Leonardo of Pisa in 1202 first published his Fibonacci sequence. In order to calculate the number of pairs of rabbits he would have at the end of a year based on their behavior of breeding, Fibonacci developed this famous sequence of numbers. Forex traders find this type of no-nonsense approach very profitable.

So you see, what many people mistakenly take as a mere mathematical abstraction, just "fooling around" with numbers, is rooted in very real-world applied mathematics. To state things very basically, the Fibonacci sequence can be used to detect and describe otherwise hidden patterns in the world around us.

How can this be applied to investing? Very astute investors understand that there are hidden patterns in the stock market--based on the mass of investors' behavior. "Buy low and sell high" and "The best time to buy is when there's blood in the streets" are but two investment aphorisms that not only work, but also come from understanding hidden patterns of the investment markets.

The reason that investment market patterns are so well hidden is because "up close" they cannot be seen. Day to day, hour to hour fluctuations in the investment markets cannot be predicted with any accuracy. But certain overall trends that extend over longer periods of time definitely can be. And savvy investors, including Forex traders, have successfully been using Fibonacci's number sequence to take advantage and make big profits.

Using the Fibonacci sequence involves a series of numbers. Each following number is the sum of the two numbers before it. It progresses like this 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, and into infinity. There are numeral interrelationships within these numerals. For example, take any number; it is roughly 1.618 times the number before it. Anciently the Greeks found number 1.618 reprehensive of the golden ratio which is the supreme essence of balance. This balance is the fundamental strategy of profitable investing

Arcs and retracements are two of the most widely used applications of the Fibonacci series by investors, including Forex traders.

A Fibonacci chart is made of three curved lines which represent support levels, key resistance and ranging. A trendline is first drawn between two points (generally the high and low points over a given period of time). Three curved lines are then drawn which intersect the trendline at the 38.2%, 50% and 61.8% points. Decisions about buying and selling are made at these points (i.e. - when the price of the commodity in question reaches these points).

Now, a retracement, in investing, refers to a reversal in the movement of a stock's price--a reversal which is enough to counter the stock's prevailing trend. Advanced successful investors pay intense attention to retracement possibilities and patterns. The Fibonacci retracement analyzes the likelihood that a financial asset's price will see a larger than average retracement and then come to support or resistance at the key Fibonacci levels before it then continues on in its original direction. A trendline is drawn between two extreme points; then, its vertical distance is divided by the key Fibonacci ratios of 23.6%, 38.2%, 50%, 61.8%, and 100%.

Traders use Fibonacci retracements to determine strategic points for placing their transactions, target prices and stop-loss points. There are other tools which use retracement techniques, chief among them Elliott Wave Theory, Gartley patterns and Tirone levels.

The "Fibonacci formula" is used in investing for the simple reason that it works. Forex traders especially seem to find huge success from using it.