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 ($\theta$).

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558 views

Use the chain rule to convert the Laplace equation in (x,y) coordinates into an equivilent differental equation in (r,theta) coordinates. [duplicate]

use the equations $r=\sqrt{x^2 +y^2}$ and $\theta=\arctan(\frac{y}{x})$. I was able to get the partial derivative of of $r$ with respect to $x$ and $y$ and the partial derivative of $\theta$ with ...
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1answer
101 views

Domain in polar coordinates

I have this domain $A=\{ (x,y) \in R^2 : x^2+y^2 \ge4, x^2+y^2-2x-2y\le0 \}$ It's right the change in polar coordinates : $$\{ (r,\theta): \theta \in [0,\frac{\pi}{2}], r \in ...
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1answer
61 views

Write in polar form

I've been giving the the following: $$z = -3e^{-i\pi/5}$$ How do I write that in polar form? I understand that -3 is not correct, since the absolute distance must be $\ge 0$. What do I need to do ...
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Complex polar co-ordinates

We know that rectangular co-ordinates $(x, y)$ can be written as a complex number $re^{i\theta}$ where $r = \sqrt{x^2 + y^2}$ and $\theta = \tan^{-1} \big(\frac{y}{x}\big)$ and $r,\theta \in ...
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3answers
40 views

Express angular position of the Earth as a function of time

Say I have for example the Earth orbiting the Sun (in circular orbit) and I want to express angular position (in radians) as a function of time. Would I be correct in thinking that $2\pi/t$ does the ...
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1answer
239 views

Find the highest point on the cardioid $r = 1 + \cos(\theta)$

I'm stuck on this. I don't know where to start! The problem: Find the highest point on the cardioid $r = 1 + \cos(\theta)$
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1answer
390 views

Perimeter of a region polar curve

I'm having some trouble with this problem: Find the length of the entire perimeter of the region inside $r = 11 \sin(\theta)$ but outside $r = 3$. I am using the formula $$\int_a^b\! \sqrt{r^2 ...
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1answer
343 views

Polar coordinate line to slope intercept form

I'm finding it very difficult to find an answer on google and in my math book on this. The question give to us is: A curve with polar equation $$ r= \frac{39}{9\sin\theta+19\cos\theta} $$ ...
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4answers
203 views

Graph r=6sin(θ)

I'm stuck on this one. I've tried converting it to Cartesian coordinates but I couldn't. I know I could figure it out by testing a bunch of values for θ, but I'd like to know how to do it a better ...
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2answers
89 views

changing $r=1+2r\cos \theta$ to its cartesian equivalent

My textbook says the polar equation, $r=1+2r\cos \theta$, its cartesian equivalent is $y^2-3x^2-4x-1=0.$ I understand that I get this if I square $r$; $r^2=x^2+y^2=(1+2x)^2.$ But don't I need to ...
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32 views

To what scope polar coordinate makes sense?

In basic calculus, one partial-differentiate a differentiable function whose domain is an open set or a closed set etc. However how formally this process works? Here is a reference : definition of ...
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1answer
32 views

Algebraic step on a trig expressiom in linear algebra

$$W = ||V||(\cos(\varphi)\cdot \cos(\theta) - \sin(\varphi)\cdot\sin(\theta), \cos(\varphi)\cdot\sin(\theta) + \sin(\varphi)\cdot\cos(\theta))$$ $$= (v_1 \cos(\theta) - v_2 \sin(\theta), v_1 ...
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0answers
73 views

Line integral of a conservative fields over a circle

I need to show that moving the curve to a simply connected region, the integral of the field over the curve will be $0$. Given $F(x, y) = ((-y)/(x^2+y^2 ), (x/(x^2+y^2 ))$, and $γ$ circle of ...
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1answer
71 views

Unable to solve any Euler questions. Fundamental error I cannot find

Good day, I have been trying to solve Euler based questions for a day now. And i realize I still cannot solve a single one, and am getting errors for all my questions. I feel like I am getting ...
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24 views

calculating position of a point knowing two reference lengths

Hi, I would like to know if there is a way to calculate a unique position for Point A knowing the lengths l1 and l2 which are variable string lengths. Point A can move within the range shown below. ...
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274 views

What is a complex number that can't be written in polar form?

What is the cartesian form of a complex number that can't be written in polar form? Why can't it be written in polar form?
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1answer
339 views

Show that $u(x)=\ln\left(\ln\left(1+\frac{1}{|x|}\right)\right)$ is in $W^{1,n}(U)$, where $U=B(0,1)\subset\mathbb{R}^n$.

The entire problem statement is: Let $n>1$ and let $U=B(0,1)\subset\mathbb{R}^n$. Show that $u:U\to\mathbb{R}$ given by $$u(x)=\ln\left(\ln\left(1+\frac{1}{|x|}\right)\right)$$ is in ...
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2answers
620 views

Find Cartesian coordinates of polar curve $r =5\sin(\theta) + 5\cos(\theta)$

Polar equation of the form $r = 5\sin(\theta) + 5\cos(\theta)$ The Cartesian equation is of the form $(x-A)^2+(y-B)^2 = R^2$ Find $A,B$, and $R$. Guess: Let $x = R\cos(\theta) + A$ and $y = ...
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3answers
209 views

How can I calculate angles between objects at the sky?

There is a polar coordinate system which represents the sky from an observer. The elevation angle is 0 to 90 degrees which corresponds to horizon to zenith. The azimuth angle is 0 degrees (north) ...
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2answers
66 views

A triangle having coordinates $(a\cos\phi, a \sin\phi) , (a\cos\theta, a\sin\theta) , (a\cos\psi, a \sin\psi)$…

A triangle having coordinates $(a\cos\phi, a \sin\phi) , (a\cos\theta, a\sin\theta) , (a\cos\psi, a \sin\psi)$ having its area $$ \Delta = 2a^2 \sin\frac{\theta - \phi}{2}\sin\frac{\phi ...
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0answers
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Alpha and Omega Limit Sets in Polar Coordinates [duplicate]

I guess here I am not sure how to get started, I know the definitions: The $ω$-limit sets of points are the set of points that the system of equation approach as time goes to infinity, and the ...
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1answer
42 views

Convert to polar and evaluate

I have $$z= x^2 + y^2$$ $$z=2x$$ I set them equal to get their intersection, I get $$2x= x^2 + y^2$$ $$0= x^2 -2x +y^2$$ by completing square I get $$y= \pm \sqrt{1-(x-1)^2}$$ I need to put ...
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1answer
26 views

Use triple to verify that a paraboloid divides a solid in two regions of the same volume, where am I wrong?

Let $S$ be the region over the $xy$ plane and inside the intersection of the cylinder $x^2+y^2=a^2$ and the plane $z=a^2$. I want to verify that the paraboloid $z=x^2+y^2$ divides $S$ into two ...
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2answers
67 views

Polar coordinates, Differentiation

Can someone clarify this step for me please, "The polar coordinate r satisfies $r^2=x^2+y^2$, so by differentiating with respect to t we get $r\cdot\dot r=x\cdot\dot x+y\cdot\dot y$" I am totally ...
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2answers
58 views

Understanding the Jacobian

I was given this problem: Use double integrals to find the area under the curve defined by $r=1+\sin\theta$. We can see that $0\leq\theta\leq2\pi,$ and $0\leq r\leq 1+\sin\theta.$ My question is, ...
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2answers
53 views

Double integral with polar?

I have the following integral : $$\iint\limits_R \operatorname e^{-\frac{x^2+y^2}{2}} \operatorname d\!y \operatorname d\!x $$ Where R is: $$R=\{(x,y):x^2+y^2 \leq 1\}$$ I think I should convert to ...
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48 views

Solve double integral

$$ \int_0^2 \int_0^{4-x^2} \frac{xe^{2y}}{4-y} \, dy\, dx $$ I'm stuck with this problem. I think I should change it so I integrate with respect to $dx \, dy$ but I'm not sure. Any help? Thanks
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1answer
40 views

Solve the double integral

I am calculating: $$ \int\int_R (2ax-x^2-y^2)^{\frac{1}{2}} \, dA$$ Where $R$ is the region determined by the inside of $x^2+y^2-2ax=0$ So far, I tried using polar coordinates, wich turns the ...
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1answer
25 views

Graphing in Polar Coordinates

I´m currently using polar coordinates to calculate some double and triple integrals. However, I have an small doubt; when you are want to express, lets say, a circle of radius $a$ centered in $(a,0)$ ...
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2answers
174 views

System of equations, limit points

This is a worked out example in my book, but I am having a little trouble understanding it: Consider the system of equations: $$x'=y+x(1-x^2-y^2)$$ $$y'=-x+y(1-x^2-y^2)$$ The orbits and limit sets ...
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1answer
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Conversion of polar coordinate differential 1-forms to xy-plane

I am new to differential geometry (and StackExchange!) and am having some trouble with the conversion of the polar differential one-forms: $dr$ and $d \theta $. How do I express these in terms of ...
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1answer
61 views

Integral by polar coordinates

How to calculate the integral $$\int_0^6\int_0^y x\;dx dy$$ using polar coordinates?$$$$I know that $x=R\cos \theta$ and $y=R\sin\theta$ and that the Jacobian is $R$.
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31 views

Specific cartesian coordinates of an ellipse

I want to do the following: 1.) Ask user for the vertical and horizontal distances of the ellipse 2.) With this information calculate the circumference 3.) Divide the circumference by the closest ...
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2answers
55 views

Better substitution calculating integral?

I'm calculating $$ \iint\limits_S \, \left(\frac{1-\frac{x^2}{a^2}-\frac{y^2}{b^2}}{1+\frac{x^2}{a^2}+\frac{y^2}{b^2}} \right)^\frac{1}{2} \, dA$$ with $$S =\left\{ (x, \, y) \in \mathbb{R}^2 : ...
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2answers
1k views

converting improper double integrals to polar form: what do I do with infinity limits

I need to convert $$ \int_{-\infty}^{\infty}\int_{-\infty}^{\infty}-e^{\frac{x^2+y^2}{5}}dA$$ To polar form. I know $x^2+y^2 = r^2, $ and $dA = rdrd\theta$ But what do I do with the $\infty$ ...
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2answers
95 views

Need help converting $z = \ln(x^2 + y^2)$ to polar

The full question is this: Volume of a solid in any region R is given by: $$\int\!\!\!\int_Rf(x,y)dydx $$ where, $$f(x,y) = z = \ln(x^2+y^2)$$ and, $$x^2+y^2=r^2$$ There for, $$dydx = ...
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0answers
113 views

What function has a 3D graph that will look like a spiral into a singularity?

I am trying to draw text spiraling into a black hole, from a more interesting slightly off-orthogonal viewpoint. I think a function that defines a black hole/singularity surface might look something ...
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0answers
26 views

Double Integral Mistake with Parametric Equation

I'm trying to figure out the mass of an object bounded by $y=0$ and $y=\sqrt{1-x^2}$ the density at a given point is proportional to its distance from the origin; $\rho(x,y) = kxy$. So I set it up ...
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0answers
147 views

Convert geodetic coordinates to cartesian coordinates

I am working on some simulation software that will represent a number of entities in a defined geographic area in the world. The part of the software that I am currently working on is to implement ...
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2answers
44 views

solve polar coordinate integral

Evaluate $$\int_0^R\int_0^\sqrt{R^2-x^2} e^{-(x^2+y^2)} \,dy\,dx$$ using polar coordinates. My answer is $-\frac{1}{2}R(e^{-R^2+x^2}-1)$ but I want to confirm if that's correct And also, when I ...
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0answers
59 views

Find arc centerpoint(x,y) with start(x,y) and end(x,y) in a conical helix

Im trying to script drawing of a conical helix in 3D software, and are stuck at the last arc when its not a full 180 degree arc. I know(calculate) the arc startpoint and endpoint, but how do I find ...
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1answer
33 views

Cartesian to Polar coordinates where alpha is real parameter

I want to convert the following equation in Cartesian form to Polar: $$-y(1+\alpha+x)+x(1-x^2-y^2)$$ so $x = r\cos(\theta)$ and $y = r\sin(\theta)$ I can get this far: ...
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1answer
33 views

Is it possible to write all of the functions in terms of polar form?

Is it possible to write all functions in terms of polar form? For example, the equation of the circle with radius one can be written like $r=1$ I'm wondering whether reform the equations of all curves ...
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2answers
108 views

Finding the Equation of a Tangent Line to a Polar Curve

Find the equation of the tangent line to the polar curve: $r=3-3\sin\theta$ at $\theta=\frac{3\pi}{4}$ I have the equation: $$\frac{dy}{dx} ...
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1answer
27 views

Tangent Line of Polar Curve

i start by changing polar coords into x and y and then find the derivatives to get the slope. $$x=(3-3\sin\theta)\cos\theta $$ $$x=3\cos\theta -3\cos\theta \sin\theta $$ and took $x'=(-3\sin\theta ...
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1answer
292 views

Transform second order partial derivatives into polar coordinates

I have the following question: Let $u(x, y)$ be a function with continuous second order partial derivatives. Use the chain rule to transform the expression: $$ x^2\frac{\partial^2u}{\partial ...
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1answer
367 views

Changing to polar form for Green's Theorem

In my text given the integral $\int_{\partial{D}} xy\,dx$, and that $$\int_{\partial{D}} xy\,dx=-\int\int_{D}x\,dx\,dy = - \int\int r\cos \theta\,r\,dr\,d\theta$$ I'm not really understanding the ...
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4answers
78 views

Limit using polar coordinates?

$$\lim_{(x,y) \to (0,0)} \frac{x y^2}{(3x^2 + 4x^2)}$$ How would one calculate above "using polar coordinates"? It was mentioned during class shortly, but we won't be introduced to this until next ...
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1answer
990 views

How to find the limits of integration to get the area for a loop of a lemniscate?

I know how to integrate the squared radius to get the equation that'll give me the area, like such for a lemniscate with $r^2=8\sin(2\theta)$ : $$1/2\int 8sin(2\theta) = 4 \int \sin(2\theta) = 4 * ...
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2answers
78 views

Divergence of vector in spherical coordinates

How should I calculate the divergence for $$\vec{V}=\frac {\vec{r}}{r^2}$$ Is it possible to convert it from spherical coordinates to cartesian?