1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Cartesian points in polar coordinates.

  1. Mar 18, 2006 #1
    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

  2. jcsd
  3. Mar 18, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    Instead of resorting to a calculator, draw the line segment from the origin to the point (3,3).
    What is the angle this line segment makes with the positive x-axis?
  4. Mar 18, 2006 #3
    lakitu, you could have done some research. That's one good thing I learned from this forum. I didn't learn yet polar coordinates and I think I can resolve this exercise by simply reading wikipedia's introduction on polar coordinates.

    See- http://en.wikipedia.org/wiki/Polar_coordinates
  5. Mar 18, 2006 #4
    your right, i guess i assumed it was a little tougher than it was :)

    to arildno: Is the angle 45 deg ? would that make the answer (3,45)

    kind regards lakitu
  6. Mar 18, 2006 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Look again at the radial component. How far is it from the origin to (3,3)?
  7. Mar 18, 2006 #6
    im not sure what you mean? i can only think the distance is 6 if its not 3 what i originally believed :)
  8. Mar 18, 2006 #7
    i read that the position of the point is defined by its direct distance from the origin (O) do you measure this with a ruler? I am just unsure :)
  9. Mar 18, 2006 #8
    lakitu, see the introduction of wikipedia and the formula to determine the radial distance from the pole and think if it really is 6 or 3 or [tex]3\sqrt{2}[/tex].
  10. Mar 18, 2006 #9


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Would you please show us the relationship between polar and cartesian coordinates.
  11. Mar 18, 2006 #10
    i found this example in my text book, r = sqrt(x*x + y*y) a = atan(y / x) which would give me the distance of 4.24 for r (the origin to 3,3)

    so would the answer be (4.24,45deg)?

    i did read your recomendations but struggled to figure those out :)

    am i on the right lines ?
  12. Mar 18, 2006 #11
    Yes. That's right. :approve:
    But you could use instead of the approximated 4.24 the precise r, which is [tex]3\sqrt{2}[/tex].
  13. Mar 18, 2006 #12
    wow at last! I think i am going to have to change my username after this topic!

  14. Mar 18, 2006 #13
    Could you explain to me how you work out that the precise r is [tex]3\sqrt{2}[/tex] ?

    Thank you
  15. Mar 18, 2006 #14


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    What is the length of the hypotenus of a right triangle when both of the other sides have length 1?
  16. Mar 18, 2006 #15
    lakitu, follow Integral's suggestion. I would have explained to you how do to it, but you would't learn as well as you will if you think for yourself.
  17. Mar 18, 2006 #16
    i get it AC^ = AB^ + BC^ :)
  18. Mar 18, 2006 #17
    no i stll dont get it:(
  19. Mar 18, 2006 #18


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Why do you use the sides of some unknown triangle, when you have a number for the lengths of the sides?
  20. Mar 19, 2006 #19


    User Avatar
    Homework Helper

    Uhmm, I suggest you reading your textbook again. There should be some chapter about the distance betweeen 2 points in Cartesian coordinate. The distance between 2 points P(xP, yP), and Q(xQ, yQ) is:
    [tex]d = PQ = \sqrt{(x_P - x_Q) ^ 2 + (y_P - y_Q) ^ 2}[/tex].
    Now apply this, adn see if you can work out [tex]r = 3 \sqrt{2}[/tex].
    Remember that the origin O is (0, 0).
    Can you go from here? :)
    Last edited: Mar 19, 2006
  21. Mar 20, 2006 #20
    You were on the right track with this. If you have a point, (3, 3), you can use this theorem to work out the length of the hypotenuse, which is the distance between (3, 3) and the origin.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Cartesian points in polar coordinates.
  1. Polar coordinate (Replies: 9)

  2. Polar Coordinates (Replies: 2)

  3. Polar coordinates (Replies: 20)