Perimeter (c): the diameter (d) of a circle. If the circumference (c) of a circle divided by the diameter (d) of the circle is equal to π, then the meaning of multiplication is equal to.

π times the diameter of the circle (d) equals the circumference of the circle (c), and c = π d.

The diameter (d) of the same circle is twice the radius (r) of the circle, so the circumference (c) of the circle is equal to 2 times π times the radius (r) of the circle, and c = 2π R. If the circle is divided into several parts, an approximate rectangle can be made.

The width of the rectangle is equal to the radius (r) of the circle, and the length of the rectangle is half the circumference (c) of the circle. The area of the rectangle is ab, and the area of the circle is: the square of the radius (r) of the circle times π,

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Extended data:

Geometric algorithm of pi

As an ancient geometric kingdom, ancient Greece made great contributions to pi. Archimedes (287-265438 BC)

Year)

For the first time in human history, the approximate value of pi is calculated theoretically. Starting from the unit circle, Archimedes first found that the lower bound of pi was 3 by inscribed regular hexagon, and then found that the upper bound of pi was less than 4 by pythagorean theorem.

Then, he doubled the number of sides of inscribed regular hexagon and circumscribed regular hexagon to inscribed regular hexagon 12 and circumscribed regular hexagon 12 respectively, and then improved the upper and lower bounds of pi with the help of Pythagorean theorem. He gradually doubled the number of sides inscribed with regular polygons and circumscribed with regular polygons until inscribed with regular polygons and circumscribed with regular polygons.

Finally, he found that the lower and upper bounds of pi were 223/7 1 respectively.

And 22/7,

And take their average 3. 14 185 1.

Is an approximation of pi. Archimedes used the concepts of iterative algorithm and bilateral numerical approximation, which is the originator of computational mathematics.

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