Wikipedia
Milú (Maria de Lourdes de Almeida Lemos) (24 April 1926 – 5 November 2008) was a Portuguese actress and singer.
The name Milü (; "detailed (approximation) ratio"), also known as Zulü ( Zu's ratio), is given to an approximation to (pi) found by Chinese mathematician and astronomer Zǔ Chōngzhī (祖沖之). He computed to be between 3.1415926 and 3.1415927 and gave two rational approximations of , and , naming them respectively Yuelü 约率 (approximate ratio) and Milü.
is the best rational approximation of with a denominator of four digits or fewer, being accurate to 6 decimal places. It is within 0.000009% of the value of , or in terms of common fractions overestimates by less than . The next rational number (ordered by size of denominator) that is a better rational approximation of is , still only correct to 6 decimal places and hardly closer to than . To be accurate to 7 decimal places, one needs to go as far as . For 8, we need .
\begin{align}\pi & \approx 3.141\ 592\ 653\ 5\dots \\\\ \frac{355}{113} & \approx 3.141\ 592\ 920\ 3\dots \\ \\ \frac{52163}{16604} & \approx 3.141\ 592\ 387\ 4\dots \\ \\ \frac{86953}{27678} & \approx 3.141\ 592\ 600\ 6\dots\end{align}
An easy mnemonic helps memorize this useful fraction by writing down each of the first three odd numbers twice: 1 1 3 3 5 5, then dividing the decimal number represented by the last 3 digits by the decimal number given by the first three digits. Alternatively, 1 / ≈ 113 / 355.
Zu's contemporary calendarist and mathematician He Chengtian ( 何承天) invented a fraction interpolation method called "harmonization of the divisor of the day" to obtain a closer approximation by iteratively adding the numerators and denominators of a "weak" fraction and a "strong" fraction. Zu Chongzhi's approximation ≈ can be obtained with He Chengtian's method