What Is a Taylor Series?
A Taylor series is a representation of a function expressed as an infinite sum of terms It is named after mathematician Brook Taylor, who developed the technique in the late 1700s. The series can be used to express real or complex functions as an expansion of the function values around a given point. It is also sometimes referred to as a Maclaurin series, which is another type of expansion. In a Taylor series, the coefficients of the expansion are determined by derivatives of the function at the selected point.
In mathematical terms, a Taylor series is expressed as:
f(x) = f(a) + (x-a)f’(a) + ½(x-a)2f”(a) + ¼(x-a)3f‴(a) + ...
Where a is the point around which expansion is desired, and f(x) is the value of the function at point x, and f’(a), f”(a) etc. are derivatives of f(x) at the selected point.
The Taylor series is useful for approximating complex functions for which the full function is difficult to calculate, or for functions that have no closed form expression.
Examples of Taylor Series
1. Exponential Function: The exponential function is f(x)=ex. The Taylor series expansion of this function is:
ex = 1 + x + ½x2 + ¼x3 + ...
2. Sine Function: The sine function is f(x)=sin(x). The Taylor series expansion of this function is:
sin(x) = x - ½x3 + ¼x5 - 1/6x7 + ...
3. Cosine Function: The cosine function is f(x)=cos(x). The Taylor series expansion of this function is:
cos(x) = 1 - ½x2 + ¼x4 - 1/6x6 + ...
4. Logarithm Function: The logarithm function is f(x) = log(x). The Taylor series expansion of this function is:
log(x) = x - ½(x-1)2 + ¼(x-1)3 - 1/6(x-1)4 + ...
5. Exponential Integral Function: The exponential integral function is f(x)=Ei(x). The Taylor series expansion of this function is:
Ei(x) = x - ½x2 + (1/3)x3 - (1/24)x4 + ...