this dynamic figure shows the graph of y = cos(x) and graphs of maclaurin polynomials from t0(x) to t40(x)…

this dynamic figure shows the graph of y = cos(x) and graphs of maclaurin polynomials from t0(x) to t40(x). use the slider to change which maclaurin polynomials tn(x) is graphed. for the figure, which of the statement is true? for any n > 1, the values of |cos(x) - tn(x)| are alternately positive and negative. for any n > 1, the values of |cos(x) - tn(x)| are never larger than 1. none of the answers is correct. for any n > 1, the values of |cos(x) - tn(x)| have no upper bound. incorrect answer

this dynamic figure shows the graph of y = cos(x) and graphs of maclaurin polynomials from t0(x) to t40(x). use the slider to change which maclaurin polynomials tn(x) is graphed. for the figure, which of the statement is true? for any n > 1, the values of |cos(x) - tn(x)| are alternately positive and negative. for any n > 1, the values of |cos(x) - tn(x)| are never larger than 1. none of the answers is correct. for any n > 1, the values of |cos(x) - tn(x)| have no upper bound. incorrect answer

Answer

Explanation:

Step1: Recall Maclaurin series property

The Maclaurin series of $\cos(x)=\sum_{k = 0}^{\infty}\frac{(- 1)^{k}}{(2k)!}x^{2k}=1-\frac{x^{2}}{2!}+\frac{x^{4}}{4!}-\frac{x^{6}}{6!}+\cdots$. The Maclaurin polynomial $T_n(x)$ is a partial - sum of this series. The error term $R_n(x)=\cos(x)-T_n(x)$ is bounded by the next - non - included term of the series according to the Alternating Series Estimation Theorem (since the Maclaurin series of $\cos(x)$ is an alternating series for non - zero $x$).

Step2: Analyze the absolute - value of the error

We know that $|\cos(x)|\leq1$ and $|T_n(x)|$ is also a well - behaved polynomial. The error $|\cos(x)-T_n(x)|$ is bounded. In fact, by the Alternating Series Estimation Theorem, for an alternating series $\sum_{k = 0}^{\infty}(-1)^{k}a_k$ ($a_k\gt0$, $a_{k + 1}\leq a_k$ and $\lim_{k\rightarrow\infty}a_k = 0$), the error $|R_N|=\left|\sum_{k = N}^{\infty}(-1)^{k}a_k\right|\leq a_N$. For the Maclaurin series of $\cos(x)$, the terms $a_k=\frac{|x|^{2k}}{(2k)!}$. The function $\cos(x)$ and its Maclaurin polynomials $T_n(x)$ satisfy $|\cos(x)-T_n(x)|\leq1$. The values of $|\cos(x)-T_n(x)|$ are not alternately positive and negative for all $n>1$ in general. And $|\cos(x)-T_n(x)|$ is bounded.

Answer:

For any $n > 1$, the values of $|\cos(x)-T_n(x)|$ are never larger than 1.