**READING: II §2 O6**
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II §2 O5

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*CHAPTER II* [:]
**
The Real Number System
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Please get the book and read along. topic index contents

The *square* of a real number a is denoted by a² and is defined to be a·a.

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For any a we have a²0, with the equality holding only if a=0; more generally the sum of the squares of several elements of is always greater than or equal to zero, with equality holding only if all the elements in question are zero. For by O5 [** positive**·

Note the special consequence 1 = 1²0.