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10.11 Finding Taylor Polynomial Approximations of Functions

Part of Infinite Sequences and Series in AP® Calculus BC. Read the opening section, then create a free account for the full interactive lesson, practice, and progress tracking.

A Taylor polynomial approximates a function near a specific center x=a using a polynomial built from the function’s derivatives at that point. The degree n Taylor polynomial for f(x) centered at a is
Tn(x)=f(a)+f′(a)(x−a)+f′′(a)2!(x−a)2+⋯+f(n)(a)n!(x−a)nT_n(x)=f(a)+f'(a)(x-a)+\frac{f''(a)}{2!}(x-a)^2+\cdots+\frac{f^{(n)}(a)}{n!}(x-a)^n
This polynomial matches the function’s value and several derivatives at x=a, which makes it a very good local approximation near that point.

You should think of Taylor polynomials as higher-order linearizations. A linearization uses the tangent line, which only matches the first derivative behavior. A Taylor polynomial goes further by matching curvature and higher-order behavior too. The closer x is to the center a, the better the approximation usually is. When a=0, the Taylor polynomial is called a Maclaurin polynomial. In BC calculus, you often build these by computing derivatives and substituting into the formula.

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