Results 1 to 4 of 4

Math Help - Magnitude of vectors question

  1. #1
    Newbie
    Joined
    Aug 2008
    Posts
    3

    Magnitude of vectors question

    Hello, I'm very relieved to have found this website!!

    I am trying to do the following question:-
    A rectangle OBCA in the xy-plane has vertices O(0,0), B(-3,4), C(5,10) and A(8.6).

    Determine the magnitude and direction of the following vectors

    1) OB
    2) OD
    I have drawn this:-



    I'm attempting part 1 and have the magnitude (which is 5) but am unsure how to work out the magnitude.

    I have the answer (it is 126.87 degrees), but this is confusing me as the triangle looks to be a right angled triangle, and so 90 + 126.87 is way over 180 degrees, so I'm clearly not working this out correctly.

    I've memorised SOC-CAH-TOA.

    Many thanks!!!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    A riddle wrapped in an enigma
    masters's Avatar
    Joined
    Jan 2008
    From
    Big Stone Gap, Virginia
    Posts
    2,551
    Thanks
    11
    Awards
    1
    Quote Originally Posted by Cheryl W View Post
    Hello, I'm very relieved to have found this website!!

    I am trying to do the following question:-
    I have drawn this:-



    I'm attempting part 1 and have the magnitude (which is 5) but am unsure how to work out the magnitude.

    I have the answer (it is 126.87 degrees), but this is confusing me as the triangle looks to be a right angled triangle, and so 90 + 126.87 is way over 180 degrees, so I'm clearly not working this out correctly.

    I've memorised SOC-CAH-TOA.

    Many thanks!!!
    The angle formed in your right triangle at the vertex of OB and the x-axis is arctan(4/3) or approx. 53.13 degrees.

    The angle that OB (terminal side) makes with the x-axis (initial side) is 180-53.13 or approx. 126.87 degrees.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    A riddle wrapped in an enigma
    masters's Avatar
    Joined
    Jan 2008
    From
    Big Stone Gap, Virginia
    Posts
    2,551
    Thanks
    11
    Awards
    1
    Quote Originally Posted by Cheryl W View Post
    Hello, I'm very relieved to have found this website!!


    I've memorised SOC-CAH-TOA.

    Many thanks!!!
    Actually, it's SOH-CAH-TOA
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Aug 2008
    Posts
    3
    Thank you masters, figured it out now.

    Will try a few more for practice.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. 3 vectors has same magnitude
    Posted in the Advanced Algebra Forum
    Replies: 5
    Last Post: January 13th 2012, 07:20 AM
  2. Sum of Magnitude of Vectors
    Posted in the Calculus Forum
    Replies: 1
    Last Post: May 7th 2010, 08:38 PM
  3. Replies: 1
    Last Post: November 21st 2009, 06:52 AM
  4. Magnitude question(Please! i am stuck)
    Posted in the Calculus Forum
    Replies: 3
    Last Post: October 26th 2009, 05:51 PM
  5. Vectors: Finding the magnitude and direction angle
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: June 7th 2009, 10:25 AM

Search Tags


/mathhelpforum @mathhelpforum