Results 1 to 4 of 4

Math Help - Formula For Rotating a Point about anotherPoint

  1. #1
    Newbie
    Joined
    Aug 2009
    Posts
    10

    Cool Formula For Rotating a Point about another Point

    Hi,

    I need to rotate a point P1(x1,y1) about a pivot point P2(x2,y2) at an angle 'a'. What is the formula for calulating the new point?

    Manu
    Last edited by ManuLi; August 19th 2009 at 05:52 AM. Reason: Correct the content
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Nov 2008
    From
    France
    Posts
    1,458
    Quote Originally Posted by ManuLi View Post
    Hi,

    I need to rotate a point P1(x1,y1) about a pivot point P2(x2,y2) at an angle 'a'. What is the formula for calulating the new point?

    Manu
    Hi

    x' = x_2 + (x_1 - x_2) \cos a - (y_1 - y_2) \sin a
    y' = y_2 + (y_1 - y_2) \cos a + (x_1 - x_2) \sin a
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    16,443
    Thanks
    1863
    Quote Originally Posted by running-gag View Post
    Hi

    x' = x_2 + (x_1 - x_2) \cos a - (y_1 - y_2) \sin a
    y' = y_2 + (y_1 - y_2) \cos a + (x_1 - x_2) \sin a
    What running-gag did was "translate" the point (x_2, y_2) to the origin (0,0) (that's the x_1- x_2 and y_1-y_2 part) then rotate about the origin, the translate back (that's why he added x_2 and y_2).
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Nov 2008
    From
    France
    Posts
    1,458
    Quote Originally Posted by HallsofIvy View Post
    What running-gag did was "translate" the point (x_2, y_2) to the origin (0,0) (that's the x_1- x_2 and y_1-y_2 part) then rotate about the origin, the translate back (that's why he added x_2 and y_2).
    Thanks, my "explanation" was a little bit short
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Rotating point about the line y=-x
    Posted in the Geometry Forum
    Replies: 2
    Last Post: December 4th 2011, 09:41 AM
  2. [SOLVED] Rotating a Point Around an Origin
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: July 8th 2011, 06:38 AM
  3. Replies: 3
    Last Post: May 27th 2010, 12:53 AM
  4. five point formula....
    Posted in the Calculus Forum
    Replies: 1
    Last Post: March 27th 2009, 03:01 AM
  5. Replies: 1
    Last Post: October 7th 2008, 02:18 AM

Search Tags


/mathhelpforum @mathhelpforum