At the core of biology and other sciences lies a problem-solving approach called the scientific method. 1  Make an observation. 2  Ask a question. 3  Form a hypothesis, or testable explanation. 4  Make a prediction based on the hypothesis.  Test the prediction.
Xi. Xi is the 14th letter of the Greek alphabet. It is pronounced in Modern Greek, and generally or in English. In the system of Greek numerals, it has a value of 60. Xi was derived from the Phoenician letter samekh. Xi is not to be confused with the letter chi, which gave its form to the Latin letter X.
Pi (symbol Ï) is a mathematical constant whose value is the ratio of any circle's circumference to its diameter in Euclidean space; this is the same value as the ratio of a circle's area to the square of its radius.(Area of a circle = Ïr2). This number is the same for every circle.i is the ratio of the circumference of a circle to its diameter. Ï is an irrational number, which means that its value cannot be expressed exactly as a fraction, Consequently, its decimal representation never ends or repeats.