Today is #PiDay in U.S…The rest of the world celebrates it on 22nd July 🙂
(Note – 22/7 is a more accurate ‘Pi’ value than 3.14).
PiDay is also the birth anniversary (144th) of Albert Einstein and the 5th death anniversary of Stephen Hawking.
π has captivated mankind for more than 4000 years…
The ancient Babylonians engraved a close approximation for it as 3.125, on a stone tablet (ca.1900 – 1680 BC). The Egyptians estimated the area of the circle by a formula that gave them 3.1605 for π. The eminent ancient greek mathematician, Archimedes, approximated the area by using Pythagorean theorem, via the area of two polygons: one polygon inscribed within the circle and a second outer one circumscribing the circle. While he did not arrive at an exact value, he knew that the actual answer lied between the areas of the polygons between the upper and lower bounds for the area of the circle. Zu Chongzhi (429–501), a brilliant Chinese mathematician and astronomer also had worked out a similar calculation.
Interestingly, it was Aryabhata, who in CE 499, in his work Arybhatiyam (Ganitapada 10), wrote
caturadhikaṃ śatamaṣṭaguṇaṃ dvāṣaṣṭistathā sahasrāṇām
ayutadvayaviṣkambhasyāsanno vṛttapariṇāhaḥ
“Add four to 100, multiply by eight, and then add 62,000. By this rule the circumference of a circle with a diameter of 20,000 can be approached.” Implying that the ratio of the circumference to the diameter is ((4 + 100) × 8 + 62000)/20000 = 62832/20000 = 3.1416, accurate to four decimal places!
ekoshapu 
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