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3.6.5 Converting Power Series to Normal Expressions

Converting power series to normal expressions.

As discussed above, power series in Mathematica are represented in a special internal form, which keeps track of such attributes as their expansion order.
For some purposes, you may want to convert power series to normal expressions. From a mathematical point of view, this corresponds to truncating the power series, and assuming that all higher-order terms are zero.

This generates a power series, with four terms.

Squaring the power series gives you another power series, with the appropriate number of terms.

Normal truncates the power series, giving a normal expression.

You can now apply standard algebraic operations.

Extracting coefficients of terms in power series.

This gives the coefficient of  in the original power series.