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The difference between the Millennium and year 2000 (378 words) |
 | The reason why the 3rd Millennium / 21st Century starts in 2001 is because there was no year 0 (or AD 0, 0 BC). |
| Because one Millennium is 1000 years, the first Millennium ends with year 1000. |
| The 21st Century and the 3rd Millennium by the U.S. Naval Observatory |
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Mathematics - MSN Encarta (1888 words) |
| Primitive counting systems were almost certainly based on using the fingers of one or both hands, as evidenced by the predominance of the numbers 5 and 10 as the bases for most number systems today. |
| There mathematics was dominated by arithmetic, with an emphasis on measurement and calculation in geometry and with no trace of later mathematical concepts such as axioms or proofs. |
| By the time of the astronomer Ptolemy in the 2nd century ad Greek mastery of numerical procedures had progressed to the point where Ptolemy was able to include in his Almagest a table of chords in a circle for steps of y°, which, although expressed sexagesimally, is accurate to about five decimal places. |
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