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teaching:topics:calculus:limits [2020/06/17 00:08] simon |
teaching:topics:calculus:limits [2022/07/26 13:19] simon |
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\(\sum\limits_{k=1}^{5}\) called "sum" which means adding together each of the values of the sequence made by setting (in this example) `k` to each integer from 1 to 5 in the expression (or function) after it ... | \(\sum\limits_{k=1}^{5}\) called "sum" which means adding together each of the values of the sequence made by setting (in this example) `k` to each integer from 1 to 5 in the expression (or function) after it ... | ||
\[W_5 = \sum_{k=1}^{5}\frac{200}{2^k}\] | \[W_5 = \sum_{k=1}^{5}\frac{200}{2^k}\] | ||
- | We are using this new variable, here `k`, like we use the index or counter in a computer program. Now we can talk about distance travelled after counting off `n` intervals in the wolf's pursuit ... | + | We are using this new variable, here `k`, like we use the index or counter in procedural computer programs. Now we can talk about distance travelled after counting off `n` intervals in the wolf's pursuit ... |
\[W_n = \sum_{k=1}^n\frac{200}{2^k}\] | \[W_n = \sum_{k=1}^n\frac{200}{2^k}\] | ||
Lastly we want to be able to write the sum if we kept adding up and somehow (?!?) included **all** of the infinite number of smaller and smaller distances: | Lastly we want to be able to write the sum if we kept adding up and somehow (?!?) included **all** of the infinite number of smaller and smaller distances: | ||
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So mathematicians invented another notation, and a new ... **very powerful!** ... idea to explore, we use notation like '\(\ \lim\limits_{n\to\infty}\ \)' for the idea of the 'limit' we spoke about above, and start our exploration by defining: | So mathematicians invented another notation, and a new ... **very powerful!** ... idea to explore, we use notation like '\(\ \lim\limits_{n\to\infty}\ \)' for the idea of the 'limit' we spoke about above, and start our exploration by defining: | ||
- | \[\sum_{k=1}^{\infty}{\rm f}(k) \defeq \lim_{n\to\infty}\sum_{k=1}^n {\rm f}(k)\] | + | \[\large\sum_{k=1}^{\infty}{\rm f}(k) \defeq \lim_{n\to\infty}\sum_{k=1}^n {\rm f}(k)\] |
===Now take time to see what we can make of all this!=== | ===Now take time to see what we can make of all this!=== | ||
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What do we mean when we write \(\quad\lim\limits_{x\to n}{\rm f}(x)\) ? | What do we mean when we write \(\quad\lim\limits_{x\to n}{\rm f}(x)\) ? | ||
- | Then ... what does it mean to write \(\quad\lim\limits_{x\to\infty}{\rm f}(x)\) ? | + | Then ... what does it mean to write \(\quad\lim\limits_{x\to\infty}\,{\rm f}(x)\) ? |
Now ... try to graph the function: \(\displaystyle\quad {\rm f}(x) = \frac{x^2-a^2}{x-a},\quad\) say when `\ a = 2` | Now ... try to graph the function: \(\displaystyle\quad {\rm f}(x) = \frac{x^2-a^2}{x-a},\quad\) say when `\ a = 2` | ||
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What about \(\quad\lim\limits_{x\to\infty}{\rm f}(x)\quad\) and \(\quad\lim\limits_{x\to -\infty}{\rm f}(x)\ \)? | What about \(\quad\lim\limits_{x\to\infty}{\rm f}(x)\quad\) and \(\quad\lim\limits_{x\to -\infty}{\rm f}(x)\ \)? | ||
+ | <WRAP right>**=>[[introduction#ideas to consider as you start calculus|motion]]**</WRAP> |