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Started NS course
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AustinTSchaffer committed May 17, 2024
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10 changes: 10 additions & 0 deletions OMSCS/Courses/Network Science/00 - Intro Notes.md
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---
tags:
- OMSCS
- NS
---
# 00 - Intro Notes

Course textbook is an online resource
- Errata: http://networksciencebook.com/translations/en/resources/NetworkScienceErrata.pdf
-
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Expand Up @@ -123,6 +123,7 @@ The answer is C. Again, this is something that is memorize-able. Doing the deriv
- $g'(x)=1/x$
- $\frac{d}{dx}\frac{f(x)}{g(x)}=\frac{(a^xln(a))(ln(x))-(1/x)(a^x)}{ln(x)ln(x)}$
- I'm not an insane person, and I don't really feel like simplifying this right now. I plugged it into an online calculator, which found that the simplification is indeed not $a^x$
- This also drives home why $e^x$ derives and integrates to itself. $ln(e)=log_e(e)=1$

## Q9: Diff-EQ
![[Pasted image 20220814155827.png]]
Expand Down Expand Up @@ -202,7 +203,7 @@ Oh thank fuck, that's one of the answers.

$A=\begin{bmatrix}-2&1\\12&-3\end{bmatrix}; \lambda=?$

$\lambda$ means "eigenvalue". You can get the eigenvalue by doing $|A-\lambda{I}|=0$. The vertical bars is the same as $\det(A-\lambda{I})$, which means to find the determinate of the matrix.
$\lambda$ means "eigenvalue". You can get the eigenvalue by doing $|A-\lambda I|=0$. The vertical bars is the same as $\det(A-\lambda I)$, which means to find the determinate of the matrix.

$\det(A-\lambda{I_2})=0$
$\det({\begin{bmatrix}-2&1\\12&-3\end{bmatrix}-\begin{bmatrix}\lambda&0\\0&\lambda\end{bmatrix})}=0$
Expand All @@ -213,7 +214,7 @@ $\begin{bmatrix}a&s\\ d&f\end{bmatrix}*\begin{bmatrix}q&w\\ e&r\end{bmatrix}=\be

$\begin{vmatrix}-2&1\\12&-3\end{vmatrix}*\begin{vmatrix}\lambda&0\\0&\lambda\end{vmatrix}=\begin{vmatrix}{-2\lambda+0}&{0+\lambda}\\ {12\lambda+0}&{0-3\lambda}\end{vmatrix}=\begin{vmatrix}{-2\lambda}&{\lambda}\\ {12\lambda}&{-3\lambda}\end{vmatrix}=0$

The determinate of a 2x2 matrix looks like:
The determinant of a 2x2 matrix looks like:

$\begin{vmatrix}a&s\\ d&f\end{vmatrix}=af-sd$

Expand Down Expand Up @@ -279,7 +280,7 @@ A singular matrix is a [square matrix](https://mathworld.wolfram.com/SquareMatri

Therefore, `A` is super false. It's the exact opposite of true.

A matrix has an inverse if the determinant is non-zero. That means `D` is not true. A 0 determinant is not negative.
A matrix has an inverse if the determinant is non-zero. That includes positives and negatives. `D` is therefore true, but not completely correct.

`B` is also not true. A matrix being symmetric doesn't have any bearing on whether it has an inverse. There do exist symmetric matrices that have determinants of 0. Check out this example

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6 changes: 6 additions & 0 deletions templates/OMSCS NS Module Notes.md
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---
tags:
- OMSCS
- AI
---
# {{title}}

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