Notices
Results 1 to 23 of 23

Thread: Polar equation exercise

  1. #1 Polar equation exercise 
    Forum Freshman Arcosseno's Avatar
    Join Date
    Jan 2019
    Location
    Brasil
    Posts
    10
    Convert to cartesian the following polar equation:

    r = asec(θ)

    If you can solve this, could you also explain your answer to me?


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Isotope
    Join Date
    Feb 2012
    Location
    Western US
    Posts
    2,819
    Quote Originally Posted by Arcosseno View Post
    Convert to cartesian the following polar equation:

    r = asec(θ)

    If you can solve this, could you also explain your answer to me?
    Forum policy does not permit us to do homework for students. We can help if you get stuck, though. What have you done to try to solve this?


    Reply With Quote  
     

  4. #3  
    Forum Freshman Arcosseno's Avatar
    Join Date
    Jan 2019
    Location
    Brasil
    Posts
    10
    I wonder why?

    I tried using my knowledge of cartesian equations (which is high school level) but I know nothing of polar equations, so I believe the problem is there.
    Reply With Quote  
     

  5. #4  
    Forum Professor river_rat's Avatar
    Join Date
    Jun 2006
    Location
    South Africa
    Posts
    1,509
    Can give you hints though, what is the relationship between x, y, r and theta? And how would you write sec as a relationship using cos or sin.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
    Reply With Quote  
     

  6. #5  
    Forum Freshman Arcosseno's Avatar
    Join Date
    Jan 2019
    Location
    Brasil
    Posts
    10
    That helped, but not enough. I'll have to find other texts on polar equations. I know r = x + y, but I can't see the bigger picture with what was presented to me (a single book)
    Reply With Quote  
     

  7. #6  
    Forum Freshman Arcosseno's Avatar
    Join Date
    Jan 2019
    Location
    Brasil
    Posts
    10
    Updating on the situation, I found out that x = rcosθ and y = rsenθ; and that secθ= 1/cosθ. But this was still not enough to find my answer. I also read on the Homework topic that updating on my situation was a good thing to do; so, that's what I'm doing.
    Reply With Quote  
     

  8. #7  
    Forum Professor river_rat's Avatar
    Join Date
    Jun 2006
    Location
    South Africa
    Posts
    1,509
    You pretty much have all the parts you need now, r = a/cos(theta) is the same as r*cos(theta) = a. Do we have a different label for r*cos(theta)?
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
    Reply With Quote  
     

  9. #8  
    Forum Ph.D.
    Join Date
    Jul 2008
    Location
    New York State
    Posts
    975
    Use r=sqrt(x^2+y^2) and cos(theta)=x/sqrt(x^2+y^2).
    Reply With Quote  
     

  10. #9  
    Forum Freshman Arcosseno's Avatar
    Join Date
    Jan 2019
    Location
    Brasil
    Posts
    10
    @mathman you can use LaTeX to write those equations in here. @river_rat I'll try now, even though I still don't have an answer for y. Gonna find it, hopefully.
    Reply With Quote  
     

  11. #10  
    Forum Freshman Arcosseno's Avatar
    Join Date
    Jan 2019
    Location
    Brasil
    Posts
    10
    I have r = xsecθ, but this still isn't a cartesian equation. Any ideas of how to find y? Thank you for your help. I tried liking your post but it won't let me.
    Reply With Quote  
     

  12. #11  
    Forum Professor river_rat's Avatar
    Join Date
    Jun 2006
    Location
    South Africa
    Posts
    1,509
    Quote Originally Posted by Arcosseno View Post
    I have r = xsecθ, but this still isn't a cartesian equation. Any ideas of how to find y? Thank you for your help. I tried liking your post but it won't let me.
    Not sure how you got there, r*cos(theta) = a is the same as x = a. so a vertical line through a.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
    Reply With Quote  
     

  13. #12  
    Forum Freshman unknown_artist's Avatar
    Join Date
    Jan 2018
    Posts
    80
    @arcosseno I am thinking on what you would do if you were asked something about toroidal and spherical coordinates...
    Reply With Quote  
     

  14. #13  
    Forum Freshman Arcosseno's Avatar
    Join Date
    Jan 2019
    Location
    Brasil
    Posts
    10
    @river_rat coordinates always (x,0)? I mean, even if it could be drawn that way, r is still xsecθ, secθ would probably define a y.

    @unknown_artist I don't know yet
    Reply With Quote  
     

  15. #14  
    Forum Professor river_rat's Avatar
    Join Date
    Jun 2006
    Location
    South Africa
    Posts
    1,509
    Quote Originally Posted by Arcosseno View Post
    @river_rat coordinates always (x,0)? I mean, even if it could be drawn that way, r is still xsecθ, secθ would probably define a y.
    I'm not sure what you are trying to convey here sorry.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
    Reply With Quote  
     

  16. #15  
    Forum Freshman Arcosseno's Avatar
    Join Date
    Jan 2019
    Location
    Brasil
    Posts
    10
    You said the function would be a vertical line through a, right? but there is a secθ in the way of that.
    Reply With Quote  
     

  17. #16  
    Forum Ph.D.
    Join Date
    Jul 2008
    Location
    New York State
    Posts
    975
    Quote Originally Posted by Arcosseno View Post
    @mathman you can use LaTeX to write those equations in here. @river_rat I'll try now, even though I still don't have an answer for y. Gonna find it, hopefully.
    By trying all possibilities I knew of, I found how latex works here - the key is [tex]. My original post becomes: Use and .
    Last edited by mathman; January 21st, 2019 at 05:08 PM.
    Reply With Quote  
     

  18. #17  
    Forum Professor river_rat's Avatar
    Join Date
    Jun 2006
    Location
    South Africa
    Posts
    1,509
    Quote Originally Posted by Arcosseno View Post
    You said the function would be a vertical line through a, right? but there is a secθ in the way of that.
    I think there is an error or two in your algebra, recheck that.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
    Reply With Quote  
     

  19. #18  
    Forum Ph.D.
    Join Date
    Jul 2008
    Location
    New York State
    Posts
    975
    Start with . Substitute the expressions I previously posted and get or .
    Reply With Quote  
     

  20. #19  
    Forum Freshman Arcosseno's Avatar
    Join Date
    Jan 2019
    Location
    Brasil
    Posts
    10
    You think the answer is ?
    Reply With Quote  
     

  21. #20  
    Forum Ph.D.
    Join Date
    Jul 2008
    Location
    New York State
    Posts
    975
    is the answer.
    Reply With Quote  
     

  22. #21  
    Forum Freshman Arcosseno's Avatar
    Join Date
    Jan 2019
    Location
    Brasil
    Posts
    10
    If then y = what? The Question stands.
    Reply With Quote  
     

  23. #22  
    Forum Professor river_rat's Avatar
    Join Date
    Jun 2006
    Location
    South Africa
    Posts
    1,509
    Quote Originally Posted by Arcosseno View Post
    If then y = what? The Question stands.
    What is the equation for a vertical line on the x-y plane?
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
    Reply With Quote  
     

  24. #23  
    Forum Ph.D.
    Join Date
    Jul 2008
    Location
    New York State
    Posts
    975
    Quote Originally Posted by Arcosseno View Post
    If then y = what? The Question stands.
    y=anything. It doesn't matter, since completely describes the function.
    Reply With Quote  
     

Similar Threads

  1. New exercise study.
    By GiantEvil in forum Health & Medicine
    Replies: 12
    Last Post: November 2nd, 2018, 03:24 PM
  2. Exercise.
    By Corporal William Cremola in forum Health & Medicine
    Replies: 13
    Last Post: July 10th, 2012, 03:32 AM
  3. Why does non-polar dissolve in non-polar?
    By maruhan2 in forum Chemistry
    Replies: 1
    Last Post: June 17th, 2010, 10:18 AM
  4. Looking for exercise books
    By 11 73 3 33 in forum Mathematics
    Replies: 2
    Last Post: May 19th, 2009, 03:41 PM
  5. The Importance of Exercise
    By heather in forum Health & Medicine
    Replies: 5
    Last Post: May 28th, 2007, 09:52 PM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •