1, given the circumference of the circle, find the diameter of the circle:
Diameter = circumference÷π (3.14)
2. Given the circumference of a circle, find the radius of the circle:
Radius = perimeter ÷ 2 ÷ π(3. 14)
The basis is: pi.
Pi is the ratio of the circumference to the diameter of a circle, which is generally expressed by the Greek letter π (pronounced pài). π is a constant (approximately equal to 3. 14 1592654), indicating the ratio of circumference to diameter. It is an irrational number, that is, an infinite cycle decimal. In daily life, pi is usually expressed as 3. 14, which is used for approximate calculation.
As we all know, pi has been "entangled" with human beings for nearly 4000 years since its birth.
π, ranked 16 in the Greek alphabet, is the first letter of Greek π ε ρ ρ ε ρ α (meaning boundary and circumference). Although it existed as early as four ancient civilizations, π has really been redefined as a universal constant for only nearly 300 years.
According to historical records, 163 1 year, π first appeared in the book "Keys to Mathematics" by mathematician William Oughtred. 1706, the British mathematician William Jones also mentioned π in his math textbook Introduction to New Mathematics.
However, at this time, the demand for π estimation is still in short supply, and it did not attract the attention of mathematics until Euler was met.
1748, Euler's masterpiece Introduction to Infinitesimal Analysis was published. In this book, Euler suggested using the symbol "π" to express pi, and directly used π in it.
Under the active advocacy of Euler, π finally became synonymous with pi.