Results 1 to 6 of 6

Math Help - Trapezium question

  1. #1
    Newbie
    Joined
    Jul 2007
    Posts
    8

    Trapezium question

    Just wondering if someone can help me with a work problem please.

    From the picture, if I only know the 6 lengths of a,b,c,d,e, & f, (the 6 vertical lengths) how can I calculate AB & CD?



    Thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Global Moderator

    Joined
    Nov 2005
    From
    New York City
    Posts
    10,616
    Thanks
    9
    I think you need more than that. How about the widths?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    9,933
    Thanks
    336
    Awards
    1
    Quote Originally Posted by emersong View Post
    Just wondering if someone can help me with a work problem please.

    From the picture, if I only know the 6 lengths of a,b,c,d,e, & f, (the 6 vertical lengths) how can I calculate AB & CD?



    Thanks
    Quote Originally Posted by ThePerfectHacker View Post
    I think you need more than that. How about the widths?
    I agree with TPH. Once you set the distance between any two of the heights you can calculate the rest.

    -Dan
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,830
    Thanks
    123
    Quote Originally Posted by emersong View Post
    Just wondering if someone can help me with a work problem please.

    From the picture, if I only know the 6 lengths of a,b,c,d,e, & f, (the 6 vertical lengths) how can I calculate AB & CD?
    Hello,

    the length of (AB) is calculated by:

    (AB)^2 = (f-a)^2 + (CD)^2

    The length of (AB) is related to the length of (DC). That means you can't calculate (AB) and (CD) independently. (Compare the previous posts of ThePerfectHacker and topsquark)
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Jul 2007
    Posts
    8
    Quote Originally Posted by ThePerfectHacker View Post
    I think you need more than that. How about the widths?
    I don't know the widths, at least they would be quite difficult to measure accurately as they are in a machine with no real datum points. I can measure between AB and CD fairly easily but it would be difficult to get a datum for the distance between any two lengths.

    I am only really interested in the relative angle between AB and CD, as these are 2 parts in a machine that move and the relative angles are important.

    I thought that if I just measure across AB and CD at any 3 or points, I would be able to fit a straight line. (Which I guess I can do manually via Visio or AutoCAD.)

    Would it help if all the lengths were at right angles to CD?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    Joined
    Apr 2005
    Posts
    1,631
    Quote Originally Posted by emersong View Post
    I don't know the widths, at least they would be quite difficult to measure accurately as they are in a machine with no real datum points. I can measure between AB and CD fairly easily but it would be difficult to get a datum for the distance between any two lengths.

    I am only really interested in the relative angle between AB and CD, as these are 2 parts in a machine that move and the relative angles are important.

    I thought that if I just measure across AB and CD at any 3 or points, I would be able to fit a straight line. (Which I guess I can do manually via Visio or AutoCAD.)

    Would it help if all the lengths were at right angles to CD?
    So you only want to know the relative angle between AB and CD. I assume this has something to the with the slope of AB if CD is horizontal.

    Let that angle be alpha.

    Get the meauments of AD and BC, and of CD.
    Slope of AB = (BC -AD) /CD
    Then, tan(alpha) = slope of AB
    Therefore, alpha = arctan[(BC -AD)/CD] ------answer.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Area Of Trapezium
    Posted in the Geometry Forum
    Replies: 5
    Last Post: January 12th 2011, 04:33 AM
  2. Trapezium
    Posted in the Geometry Forum
    Replies: 2
    Last Post: December 19th 2010, 12:42 PM
  3. Trapezium solving
    Posted in the Geometry Forum
    Replies: 1
    Last Post: April 23rd 2010, 10:48 AM
  4. trapezium
    Posted in the Geometry Forum
    Replies: 1
    Last Post: December 7th 2009, 02:24 AM
  5. Need help with CONGRUENCY!! (trapezium) @___@
    Posted in the Geometry Forum
    Replies: 1
    Last Post: November 30th 2007, 04:37 AM

Search Tags


/mathhelpforum @mathhelpforum