Exponentials bearbeitet, rotes Bullet für item

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Sven Riwoldt
2024-06-29 08:27:20 +02:00
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These formulas should be memorized, both in their long polynomial form and their more concise summation notation form.
\subsection*{Example}
Use Euler's formula to show that $e^{i \pi}=-1$. Answer
Use Euler's formula to show that $e^{i \pi}=-1$. \hyperref[ExponentialsAnswer1]{Answer}
\subsection*{Example}
Compute $1-\frac{\pi^2}{2!}+\frac{\pi^4}{4!}-\cdots$. Answer
Compute $1-\frac{\pi^2}{2!}+\frac{\pi^4}{4!}-\cdots$. \hyperref[ExponentialsAnswer2]{Answer}
\subsection*{Example}
Check that taking the derivative of the long polynomial for $\sin x$ gives the long polynomial for $\cos x$ (hence, verify that $\frac{d}{d x} \sin x=\cos x$ ). Answer
Check that taking the derivative of the long polynomial for $\sin x$ gives the long polynomial for $\cos x$ (hence, verify that $\frac{d}{d x} \sin x=\cos x$ ). \hyperref[ExponentialsAnswer3]{Answer}
\subsection*{Example}
Show that the long polynomial for $e^x$ satisfies the first property above, namely $e^{x+y}=e^x e^y$. Hint: start with the long polynomials for $e^x$ and $e^y$ and multiply these together, and carefully collect like terms to show it equals the long polynomial for $e^{x+y}$. Answer
Show that the long polynomial for $e^x$ satisfies the first property above, namely $e^{x+y}=e^x e^y$. Hint: start with the long polynomials for $e^x$ and $e^y$ and multiply these together, and carefully collect like terms to show it equals the long polynomial for $e^{x+y}$. \hyperref[ExponentialsAnswer4]{Answer}
\section{More on the long polynomial}
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\end{aligned}
$$
Each polynomial in the sequence is, in a sense, the best approximation possible of that degree. Put another way, taking the first several terms of the long polynomial gives a good polynomial approximation of the function. The more terms included, the better the approximation. This is how calculators compute the exponential function (without having to add up infinitely many things).
Each polynomial in the sequence is, in a sense, the best approximation possible of that degree. Put another way, taking the first several terms of the long polynomial gives a good polynomial approximation of the function. The more terms included, the better the approximation. This is how calculators compute the exponential function (without having to add up infinitely many things).
\begin{figure}[h]
\centering
\includegraphics[width=0.7\linewidth]{ExponentialApproximants}
% \caption{}
\label{fig:exponentialapproximants}
\end{figure}
\section{EXERCISES}
\begin{itemize}
\item[\textcolor{red}{\tikzcircle{3pt}}] So, how good of an approximation is a polynomial truncation of $e^{\text {? }}$. Use a calculator to compare how close $e$ is to the linear, quadratic, cubic, quartic, and quintic approximations. How many digits of accuracy do you seem to be gaining with each additional term in the series?
\end{itemize}
%-
%- Now, do the same thing with $1 / e$ by plugging in $x=-1$ into the series. Do you have the same results? Are you surprised?
%- Calculate the following sum using what you know:
%$$
%\sum_{n=0}^{\infty}(-1)^n \frac{(\ln 3)^n}{n!}
%$$
%- Write out the first four terms of the following series
%$$
%\sum_{n=0}^{\infty}(-1)^n \frac{\pi^{2 n}}{2^n n!}
%$$