What is Polar coordinates: Definition and 585 Discussions

In mathematics, the polar coordinate system is a two-dimensional coordinate system in which each point on a plane is determined by a distance from a reference point and an angle from a reference direction. The reference point (analogous to the origin of a Cartesian coordinate system) is called the pole, and the ray from the pole in the reference direction is the polar axis. The distance from the pole is called the radial coordinate, radial distance or simply radius, and the angle is called the angular coordinate, polar angle, or azimuth. The radial coordinate is often denoted by r or ρ, and the angular coordinate by φ, θ, or t. Angles in polar notation are generally expressed in either degrees or radians (2π rad being equal to 360°).
Grégoire de Saint-Vincent and Bonaventura Cavalieri independently introduced the concepts in the mid-17th century, though the actual term polar coordinates has been attributed to Gregorio Fontana in the 18th century. The initial motivation for the introduction of the polar system was the study of circular and orbital motion.
Polar coordinates are most appropriate in any context where the phenomenon being considered is inherently tied to direction and length from a center point in a plane, such as spirals. Planar physical systems with bodies moving around a central point, or phenomena originating from a central point, are often simpler and more intuitive to model using polar coordinates.
The polar coordinate system is extended to three dimensions in two ways: the cylindrical and spherical coordinate systems.

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  1. M

    Finding the volume under a plane and region (polar coordinates)

    Hey I am trying to compute the volume of the region under the plane z=7 x + 4 y + 34 and over the region in the xy -plane bounded by the circle x^2+y^2=4 y. i can't seem to get it... like i i know that the circle is x^2+(x-2)^2=4 so 0<r<2 and 0<theta<2pi this is what i try double integral of...
  2. R

    Caucy-Riemann in polar coordinates question

    I'm well out of school, and brushing up on math/physics as a hobby. My question is if there is an intuitive explanation for the exp(I*theta) factor? From Shankar, dz = (dr+ir*d(theta))*exp(I*theta) Here's a good derivation of CR equations in polar...
  3. K

    Finding Area in Polar Coordinates

    The problem is to find the area of r = 4cos3θ. I know the formula for finding the area in polar coordinates is ∫ (from α to β) ½r²dθ. I substituted into this formula the given equation and got: A = ½ ∫ (from 0 to 2π) (4cos3θ)²dθ = ½ ∫ (from 0 to 2π) (16cos²9θ)dθ = 8 [(9/2)θ +...
  4. T

    Kinetic energy in polar coordinates

    if i have a system that I'm describing using polar coordinates, do i need to have an additional term for rotational kinetic energy? it would seem like this is covered since my velocity is in terms of the r and theta basis vectors. (i.e. i will have a term that covers the rotational movement ala...
  5. N

    Arclength in polar coordinates

    I am working on a problem regarding arclength-which asks to find the arclength for r=2-2sinx (x=theta) I worked out the integral to the integral of the square root of 8-8sinx but i didnt know how to integrate from there--any help? Thanks -nate808
  6. S

    Work in rectangular and polar coordinates: result is not the same?

    I'm a little puzzled with the work of a force considering rectangular and polar coordinates. In rectangular coordinates we have: (1) [F]=(Fx [i] + Fy [j]) is the force vector. (2) [dr]=(dx [i] + dy [j]) is small displacement. Then the work is: (3) W = [F] [dr] = (Fx dx + Fy dy) In...
  7. 4

    Area of Grass for Tied Goat: 40.4383m^2

    http://i10.tinypic.com/3ztgdx2.jpg Consider a pasture bordering on a straight river. At 2m from the river, a goat is tied to a pole with a 4m long rope. What is the area of grass that the goat can graze? The answer i got is about 40.4383m^2 Am i correct?
  8. J

    Surface Area in Polar Coordinates

    Find the surface area of the surface z=cosh(sqrt(x^2+y^2)) above the region in the xy plane given in polar coordinates: r is between 0 and theta theta is between 2 and 4 Ok. I used the formula: Surface area equals the square root of the partial derivative of x squared plus the partial...
  9. D

    Why Do I Need an Integrating Factor for Polar Coordinates?

    I'm solving the following equation in the unit square using finite differences: epsilon(u_xx+u_yy)+u_x+u_y=0, where epsilon is a singular perturbation parameter. I need to use domain decomposition to isolate the corner singularity in the outflow corner. My subdomain in this corner is a...
  10. D

    Double Integral in Polar Coordinates problem

    I am having trouble with this seemingly easy problem. Evaluate the double integral (sin(x^2+y^2)) , where the region is 16=<x^2+y^2=<81. I find the region in polar coordinates to be 4=<r=<9 0=<theta=<2pi I find the expression to be sin(rcos^2theta+rsin^2theta) r dr dtheta , which is...
  11. L

    Cartesian points in polar coordinates.

    Hey everyone, my lecture has given me this question, I am unsure where to start with it. Express the Cartesian point (3, 3) in polar coordinates. Do i need to use the sin and cos on my calc. Any help would be very helpful lakitu
  12. andrevdh

    Understanding Orbital Motion with Polar Coordinates

    I'm a bit unclear about the description of orbital motion in a plane by using the polar coordinates (r,\theta). This coordinate system changes its orientation in the inertial reference frame, that it is rotating as the orbiting object moves along its path. In the derivation of the equations of...
  13. K

    Bit of a problem with polar coordinates.

    Bit of a problem with polar coordinates. (Only trig knowledge needed.) Right. So, in this problem, I'm given the polar coordinate point (rad2, 4.39) -- "rad2" being, naturally, short for radical 2. I'm to find the rectangular coordinates of the point, using the formulas: x = r cos Theta...
  14. S

    Polar coordinates from rectangle

    Heres where I am struggling, I can't seem to change equations from rectangular to polar and vice versa an example x^2+y^2-2ax=0 heres what I got when I tried r=2a cos theta and that's a graph of a rose curve, I think, I am about 10% sure on that answer heres an example of one I...
  15. M

    MATLAB Plotting a Curve in Polar Coordinates Using MATLAB

    Ok, so I've been given a curve in polar coordinates. I came up with a parameterisation: x(t)=rcos(theta) y(t)=rsin(theta) But now I have to plot the graph using MATLAB and I have no idea. Theta lies between 0 and 2pi. This is what I put in and got back in matlab: >> t=[0:pi/50:2pi]...
  16. A

    Can Schrodinger's Equation be Transformed into Spherical Polar Coordinates?

    how do you change the schrodinger's equation into the spherical polar coordinates?
  17. W

    Can Vector Operations Be Done in Polar Coordinates?

    Do you think you could do vector operations in polar coordinates?
  18. H

    Mathematica Heat Equation in Polar coordinates in Mathematica

    Hi! Can someone please help? I'm trying to solve the heat equation in polar coordinates. Forgive my way of typing it in, I'm battling to make it look right. The d for derivative should be partial, alpha is the Greek alpha symbol and theta is the Greek theta symbol. du/dt =...
  19. C

    To understand polar coordinates

    Please I need help about polar coordinates. I have this expression: \int_0^{\infty}\int_0^{\infty}e^\frac{-(t^2 + u^2)}{2}dtdu.. Now they say: "Let's convert to polar coordinates. Define t = r cos \theta, u = r sin \theta. Then t^2 + u^2 = r^2 (this is OK) and dtdu = rd \theta dr...
  20. D

    Polar Coordinates: Show Acceleration Angle of 30°

    A particle P describes the curve with polar equation r = a e^{\theta \sqrt{3}} \cosh 2\theta in such a manner that the radius vector from the origin rotates with uniform angular speed \omega. Show that the resultant acceleration of the particle at any instant makes an angle of 30 degrees in the...
  21. B

    How do I correctly convert to polar coordinates when evaluating integrals?

    Hi, I'm having problems with converting to polar coordinates when evaluating integrals. Here is an example, it comes down to writing the following equality. After that the evaluation of the intergral is straight forward. \int\limits_0^2 {\int_{ - \sqrt {4 - y^2 } }^{\sqrt {4 - y^2 } } {x^2...
  22. quasar987

    Polar Coordinates: A Nicer Way to Define?

    As I understand it, the polar coordinates of a point is defined by the rectangular coordinates of that point according to the transformation T from R² to R² defined by T:(x,y)\mapsto (\sqrt{x^2+y^2},tan\left(\frac{y}{x}\right)) But this definition fails for y=pi and x=2 because tan(pi/2)...
  23. T

    Cross product of polar coordinates

    When using cartesian coordinates, I use the following expressions to calculate the cross product of the basis vectors: i \times j = k j \times k = i k \times i = j j \times i = -k k \times j = -i i \times k = -j Can I do the same in polar coordinates? How could I write the cross...
  24. A

    Uniqueness/ Non-uniquenss of Cartesian & Polar Coordinates

    What is the difference in the "uniqueness" of the representations of Cartesian coordinates and in polar coordinates? :confused: Also, what is the non-uniqueness?
  25. V

    Converting into polar coordinates for integration

    Another problem that I cannot figure out. Convert the follorwing into polar coordinates: \int_{-1}^{1} \int_{-\sqrt{1 - y^2}}^{\sqrt{1 - y^2}} ln\left(x^2 + y^2 + 1\right) dx\;dy I did this so far: ln\left(x^2 + y^2 + 1\right) = ln\left(r^2 + 1\right) \sqrt{1 - y^2} = \sqrt{1 - r^2...
  26. C

    Vector Operations In Polar Coordinates?

    Is it possible to do vector operations in polar coordinates?
  27. C

    Vector operations in polar coordinates?

    Is it possible to do vector operations in polar coordinates?
  28. V

    Arclength in polar coordinates?

    You know this should be simple but it's just not. A friend asked me this earlier and I was unable to disprove him. We're all aware of how one derives the area of a polar equation.. it's \pi r^2 \frac {\theta}{2 \pi} and make theta infinitely small and integrate. Why can't a similar process...
  29. P

    Vector Operations in Polar Coordinates?

    Do you think you could do vector operations in polar coordinates?
  30. P

    Cartesian and Polar Coordinates

    What are the differences in the "uniqueness" of the representations in Cartesian coordinates and in polar coordinates?
  31. D

    Need Help: Cartesian to Polar Coordinates

    Just got back into physics after 4 years in social science and I have forgotten how to convert cartesian coordinates to polar coordinates. The textbook I have makes no metion of it. probably bc I am expected to know this, but I can't remember. I remember how to calculate the distace between two...
  32. C

    Adding/subtracting in polar coordinates?

    How do you add or subtract in polar coordinates if not given the rectangular coordinates? Thanks.
  33. I

    Vector in cylindrical polar coordinates

    The problem is: Write the vector V=i+j+k=(1,1,1) at the point (x,y,z)=(1,1,1) in cylindrical polar coordinates. What is the gradient of the function phi=x(x^2+y^2)z at this point? Answer: I don't know how to write the vector in cylindrical polar coordinates. I know that the coordinates...
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