Xavier Gourdon and Pascal Sebah have created this great informational site dedicated to mathematical, algorithmic and historical aspects of some classical mathematical concepts. Several programs are offered for downloading and everything comes with easy to understand explanations.
Free Online Mathematical Constants Textbooks
In the field of mathematics, there are special numbers refereed to as mathematical constants. These numbers have often been assigned a symbol as a sort of shorthand to represent them. The reason mathematicians have assigned symbols to these numbers is because they generally include a substantial amount of numbers after the decimal point – often far beyond what the typical mathematics student would ever require. For example, most students refer to pi (the ratio between the circumference and diameter of a circle) as having a value of 3.1415 but the current record for the decimal expansion of π, if verified, stands at 5 trillion digits; obviously a level of specificity that few math students will ever require.
There are a number of sites which provide a quick reference tool for those math students requiring a greater level of precision when using one of the standard mathematical constants.
These are certainly not online textbooks but being able to find these numbers out to the desirable number of significant digits is important for any serious math student.
The Number e to 1 million places
Catalan’s Constant to 300,000 decimals
The Golden Mean – to 1 million digits.
Square Root of 2 – this one seems beyond what the typical math student would require but it is the square root of 2 to 5 million digits (yes, that’s not a misprint, 5 million)
Square Root of 3 – out to over 1 million digits.
Square Root of 5 – out to over 1 million digits.