Lay a string over the circle as closely as you can. Mark the string off where it circles back around, and then measure the string length with a ruler.
π=(4/1)-(4/3)+(4/5)-(4/7)+(4/9)-(4/11)+(4/13)-(4/15) ⋯ Take 4 and subtract 4 divided by 3. Then add 4 divided by 5. Then subtract 4 divided by 7. Continue alternating between adding and subtracting fractions with a numerator of 4 and a denominator of each subsequent odd number. The more times you do this, the closer you will get to pi.
π=3+4/(2·3·4)-4/(4·5·6)+4/(6·7·8)-4/(8·9·10)+4/(10·11·12)-4/(12·13·14) ⋯ For this formula, take three and start alternating between adding and subtracting fractions with numerators of 4 and denominators that are the product of three consecutive integers which increase with every new iteration. Each subsequent fraction begins its set of integers with the highest one used in the previous fraction. Carry this out even a few times and the results get fairly close to pi.
Scientists and mathematicians have not figured out a way to calculate pi exactly, since they have not been able to find a material so thin that it will work to find exact calculations. [10] X Research source
π=｛arcsin[√(1 - x²)]+ abs[arcsin x]｝·2. Arcsin refers to the inverse sine in radians Sqrt is short for square root Abs is short for absolute value x^2 refers to an exponent, in this case, x squared.
