Page:Elementary algebra (1896).djvu/451

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433
ALGEBRA
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433

In this series write 1 + x for a; thus (1 + x)^r


Also by the Binomial Theorem, when y < 1 we have


Now in (2) the coefficient of y is


that is.

Equate this to the coefficient of y in (1); thus we have


This is known as the Logarithmic Series.

540. Except when x is very small the series for \log_e (1 +x) is of little use for numerical calculations. We can, however, deduce from it other series by the aid of which Tables of Logarithms may be constructed.

541. In Art. 539 we have proved that


changing x into -x, we have


By subtraction,


Put \frac{1+x}{1-x}=\frac{n+1}{n} so that x = \frac{1}{2n+1} we thus obtain