Results 1 to 2 of 2

Math Help - Rotate a line about a point

  1. #1
    Newbie
    Joined
    Aug 2009
    Posts
    10

    Cool Rotate a line about a point

    Hi

    I have a line with end points (x1,y1) and (x2,y2). If I rotate a line about the point (x3,y3) at an angle 'a', it wlll be parallel to x axis. At what angle should I rotate the line about another point (x4,y4), to make it parallel to the x axis?

    Is there any formula for calculating the angle for rotating the line about the point (x4,y4)?

    Manu
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,830
    Thanks
    123
    Quote Originally Posted by ManuLi View Post
    Hi

    I have a line with end points (x1,y1) and (x2,y2). If I rotate a line about the point (x3,y3) at an angle 'a', it wlll be parallel to x axis. At what angle should I rotate the line about another point (x4,y4), to make it parallel to the x axis?

    Is there any formula for calculating the angle for rotating the line about the point (x4,y4)?

    Manu
    1. Do you mean maybe
    At what angle should I rotate the line about another point (x4,y4), to make it parallel to the y axis?
    2. If not: If the line isn't parallel to the x-axis and you know one specific angle a which produces a parallel to the x-axis then any arbitrary point will serve as center of the rotation. You'll get a parallel to the x-axis, only the place, where this parallel will be, is changing.

    The line has the endpoints A and B;
    the red point P_1 produces a parallel line to the x-axis (drawn in red)
    an the blue point P_2 produces a parallel line to the x-axis different from the first parallel.

    As you can see your angle a has the same value (but the opposite direction) as the angle formed by the original line and a parallel to the x-axis.
    Attached Thumbnails Attached Thumbnails Rotate a line about a point-rotline_umpkt.png  
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Move and Rotate a point around a new origin
    Posted in the Advanced Applied Math Forum
    Replies: 24
    Last Post: February 25th 2011, 03:33 AM
  2. Replies: 2
    Last Post: June 8th 2010, 05:59 PM
  3. Rotate a rectangle with respect to a point
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: August 20th 2009, 03:13 AM
  4. [SOLVED] Rotate about a pivot point
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: August 4th 2009, 07:48 AM
  5. Using sin and cos to rotate a point
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: September 10th 2007, 10:07 AM

Search Tags


/mathhelpforum @mathhelpforum