From 7673ba24aaf7871e846146ce9b7690b830560ea5 Mon Sep 17 00:00:00 2001 From: Maciej Topyla <m.m.topyla@student.tudelft.nl> Date: Sat, 3 Sep 2022 17:11:01 +0000 Subject: [PATCH] trying to fix reference to equations --- src/2_coordinates.md | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/src/2_coordinates.md b/src/2_coordinates.md index 16462e9..a2ca177 100644 --- a/src/2_coordinates.md +++ b/src/2_coordinates.md @@ -70,7 +70,7 @@ the angular coordinate $\varphi$ is dimensionless. <figure markdown>  - <figcaption>In this example of a polar plot, you can distinguish the radial coordinate (0.2, 0.4 etc.) \\from the angular one expressed in degrees ($0^\circ$, $45^\circ$ etc.).</figcaption> + <figcaption>In this example of a polar plot, you can distinguish the radial coordinate (0.2, 0.4 etc.) from the angular one expressed in degrees ($0^\circ$, $45^\circ$ etc.).</figcaption> </figure> @@ -90,7 +90,7 @@ $$\begin{equation} y = r \sin \varphi.\end{equation}$$ The inverse relation is given as: !!! info "Inverse relation between polar and Cartesian coordinate systems" - $$\begin{equation} r=\sqrt{x^2 + y^2}; \label{rxy}\end{equation}$$ + \begin{equation} r=\sqrt{x^2 + y^2}; \label{rxy}\end{equation} \begin{equation} \varphi=\begin{cases} \arctan(y/x) & \text{$x>0$,}\\ \pi + \arctan(y/x) & \text{$x<0$ and $y>0$,}\\ @@ -117,7 +117,10 @@ If we consider two points which are *very close*, the analysis simplifies however. We can use the geometry of the problem to find the distance (see the figure below). - +<figure markdown> +  + <figcaption></figcaption> +</figure> When going from point 1 to point 2, we first traverse a small circular arc of radius $r_1$ and then we move a small distance radially outward @@ -161,7 +164,7 @@ understood: the area swept by an angle difference $d\varphi$ <iframe width="100%" height=315 src="https://www.youtube-nocookie.com/embed/NGQWGx71w98?rel=0" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe> -Often, in physics important equations involve derivatives given in terms +Important equations in physics often involve derivatives given in terms of Cartesian coordinates. One prominent example are equations of the form $$\left(\frac{\partial^2}{\partial x^2} + \frac{\partial^2}{\partial y^2}\right) f(x, y) = \ldots.$$ @@ -169,7 +172,7 @@ The derivative operator $\left(\frac{\partial^2}{\partial x^2} + \frac{\partial^2}{\partial y^2}\right)$ is so common it has its own name: the Laplacian (here for two-dimensional space). -Such an equation is universal, but for particular situations it might be +This equation is universal, but for particular situations it might be advantageous to use a different coordinate system, such as polar coordinates for a system with rotational symmetry. The question then is: How does the corresponding equation look like in a different coordinate system? @@ -178,7 +181,7 @@ There are different ways to find the answer. Here, we will focus on directly deriving the transformed equation through an explicit calculation involving the chain rule for a function of several variables. -!!! info Chain rule for a multi-variable function +!!! info "Chain rule for a multi-variable function" Let $f$ be a function of $n$ variables: $f(y_1, y_2, \ldots, y_n)$, as well as $g_i(x_1, x_2, \ldots, x_n)$ for $i=1,2,\ldots, n$. Then -- GitLab