Kang Po (late 13th century – early 14th century) was a famous astronomer and a mathematician in Koryo.
He found a solution to a biquadratic equation which was not found until the 19th century in Europe. Thus, he made the most advanced and correct calendar in the world of those days “Susiryok” (a primitive calendar) and even a numeration table for easy correction of them.
Those days when farming held an overwhelming proportion in the economy, it was of vital importance to make a calendar that showed correct subdivisions of the seasons.
At that time people used a lunar calendar where there were 354.370 5 days in a year, so after 33 years there was a gap of about 1 year between solar and lunar calendars. Therefore, it was impossible to figure out which season a particular month belonged to.
In order to overcome this shortcoming, lunar calendars had to undergo a huge mathematical calculation for the correction of seasons
Nevertheless, limited mathematical knowledge of those times made it difficult to upgrade calendars every year.
Kang Po, who passed the state examination in 1294, volunteered to shoulder the heavy burden of making a calendar.
He made a correct calculation of the orbit of the sun according to the 24 divisions of the year, on the basis of which he succeeded in making a new correct calendar called “Susiryok”
Not satisfied with this, he decided to find a system of calculation for easy and constant correction of existing calendars.
With painstaking studies and efforts, he discovered his own original formula which is now known as x4＋ax2＋bx＋c＝0, and formed a numeration table “Susiryokripsong” necessary for calendar correction.
People in the neighbouring countries expressed their admiration and envy, saying that this was the very world-shaking miracle and that Koryo was a great power of culture.
The Yuan Dynasty not only introduced his new Susiryok as it was but also published his numeration table in the book “Taedongthonggwe”.
Having devoted all his life to improving a calendar, he wrote a book “Susiryokchopbopripsong”, where he made known the secrets of his calendar in 1343.
This is the oldest one of all the astronomy books known to the world so far.
It was not until the 19th century that Hono, a British mathematician, obtained a biquadratic equation. Kang Po was indeed a world-famous astronomer and a great mathematician.
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