Questions tagged [polar-coordinates]
Questions on polar coordinates, a coordinate system where points are represented by their distance from the origin ($r$) and the angle the line joining the point and the origin makes with the positive horizontal axis ($\theta$).
3,450 questions
0 votes
0 answers
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Unit Vectors in Polar Coordinate System [closed]
What is the need for different sets of unit vector for different locations (positions) in Polar Coordinate System ? Just as the two fixed unit vectors in Cartesian Coordinate System, why cannot we ...
17 votes
3 answers
403 views
Why does every rose curve contain a regular polygon?
I was playing around in Desmos looking at rose-shaped curves, a family of curves with polar equation $$ r = \cos n \theta, \ \ \ \ \ n \in \mathbb{N}. $$ The number of petals on this rose-curve is ...
1 vote
0 answers
32 views
The Jacobian and Integration of $n$-dimensional polar coordinates
This is my first proof and is most likely going to be crude. Please while reading comment tips about ways to improve my writing. Polar coordinates are transformed through: $$x=r\cos(\theta) \qquad y=r\...
1 vote
1 answer
149 views
How do I prove the change of variables into polar coordinates using measure theory?
From this answer I have that $ \int_Yf(y)\,\mathrm{d}(g\mu)(y)=\int_Xf(g(x))\,\mathrm{d}\mu(x)$, where $g$ is a map between measurable spaces and $g\mu$ is the image measure. With $X=[0,r]\times[0,2\...
0 votes
2 answers
52 views
If an operator is invariant with respect to 2D rotation, is it also invariant with respect to 3D rotation?
Problem: For a function $f(x,y,z)$ and a rotational change of coordinates $(x,y,z)\to (u,v,w)$, the following relation holds $$\frac{\partial^2 f}{\partial x^2}+\frac{\partial^2 f}{\partial y^2}+\frac{...
2 votes
0 answers
46 views
How to overcome Cartesian/Polar round trip anomalies in 64-bit IEEE floating-point numbers
I'm working with a scriptable 3-D rendering tool that, due to various rounding and binary representation errors in point arithmetic will throw errors at extremely rare but always inopportune times. ...
3 votes
0 answers
94 views
Drawing a smooth curve with the least maximum curvature from a point within a circle to its boundary
Given a circle with radius $r$ centered on the origin at (0,0) and, in polar coordinates: a start point, at radial distance $p$ (with $ 0 < p < r$) from the origin, and angle $\alpha$ an end ...
0 votes
1 answer
83 views
Use $\operatorname{Arg}(z)$, $\vartheta$ or $\arg(z)$ for the angle $\varphi$ in the polar form $w = r e^{i \varphi}$
Supposing to have the complex number $$z=-4 - 8 i$$ Having \begin{equation} \varrho = |z| = \sqrt{(-4)^2 + (-8)^2} = \sqrt{16 + 64} = \sqrt{80} = 4 \sqrt{5} \end{equation} \begin{equation} \arctan\...
-1 votes
2 answers
214 views
Find the $n^{th}$ Derivative of $\tan^{-1}\left(\frac{2x}{1-x^{2}}\right)$ in terms of polar coordinates of $x$ [closed]
Find the $n^{th}$ Derivative of $$f(x)=\tan^{-1}\left(\frac{2x}{1-x^{2}}\right)$$ in terms of polar coordinates $(r,\theta)$ of $x=re^{i\theta}$. My Approach $$f(x)=\tan^{-1}\left(\frac{2x}{1-x^{2}}\...
1 vote
2 answers
119 views
Expressing $\frac{\sqrt{2} + j\sqrt{2}}{1 + j\sqrt{3}}$ in its polar form
I have a complex number in cartesian form that I am trying to express in polar form. I haven't seen a form like this before but I assumed I would be able to solve it by multipyling the denominator and ...
5 votes
0 answers
97 views
Does the butterfly property characterize conics (including degenerate)?
Let $K\subset \mathbb{RP}^2$ be closed, convex set that does not contain a whole line, and is not all of $\mathbb{RP}^2$ with nonempty interior. Let $\gamma=\partial K$ be a $C^3$ curve. Then for any ...
0 votes
0 answers
43 views
Asymptote of $r \log_e(\theta)=a$
I need to find the asymptote of $r \log_e(\theta)=a$ I understand what is going on. As $\theta$ goes from $0^+$ to $1$, $r$ goes from $0^-$ to $-\infty$. I tried to write the equation as a function of ...
3 votes
2 answers
254 views
Limit of 2 variable function with exponential function
Compute the limit (if exists) $$\lim_{(x,y)\rightarrow (0,0)}e^{\frac{-y^2}{x^4}}\sqrt[3]{y}.$$ My attempt: We can pass through polar coordinates: $$\Bigg\lvert e^{\frac{-\sin^{2}(\theta )}{\rho^{2}\...
0 votes
1 answer
49 views
Radially outward tangent of polar curve
The slope of a polar function $f$ is generally given by the formula $f'(x) = \frac{f'(\theta)\sin(\theta) + f(\theta)\cos(\theta)}{-f(\theta)\sin(\theta) + f'(\theta)\cos(\theta)}$ However, the rate ...
1 vote
1 answer
57 views
In $\Bbb{R}^2\setminus\Bbb{D}^2$ with warped metric write the limit of θ-coordinate as the geodesic reaches the boundary in terms of initial data
In the manifold $$ M=\{x\in\mathbb{R}^2:\ |x|>a\}\quad(a>0), $$ you can write $M\cong (a,\infty)\times S^1$ with polar coordinates $(s,\theta)$ and take a conformal rescaling of the Euclidean ...