Results 1 to 2 of 2

Math Help - vectors, normal to the plane

  1. #1
    Newbie
    Joined
    Jan 2007
    Posts
    18

    vectors, normal to the plane

    Find the normal vector to the plane which is
    a) parallel to 4i-2j+2k and i+3j+3k

    b) passes through the points O(0,0,0), P(1,-1,2) and Q(3,2,-1)

    These are two seperate questions,

    for a) i tried using the cross product for the two vectors seperately with a variable of n(xi + yj +zk) and trying to solve the two equations simultaeneously but i realise we have no constants in the equations! I don't know how to tackle the second. Please help i dont understand vectors.

    p.s. my maths exam is tomorrow and then i will (try and) never bother you guys again! I am not going to do maths at uni thank the lord.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,807
    Thanks
    116
    Quote Originally Posted by mathshelpneeded View Post
    Find the normal vector to the plane which is
    a) parallel to 4i-2j+2k and i+3j+3k
    Hello,

    you are only asked to calculate the direction of the plane not the equation of a specific plane. Therefore your method is OK. You should have got:
    n = -12i + -10j + 14k

    Quote Originally Posted by mathshelpneeded View Post
    b) passes through the points O(0,0,0), P(1,-1,2) and Q(3,2,-1)
    The plane runs through the point O and the vectors OP and OQ define the plane:

    p = (0i + 0j + 0k) + r(i - j - 2k) + s(3i + 2j -k), r,s in IR

    If you want to use the normal vector (-3, 7, 5) then the equation of the plane becomes:
    -3x + 7y + 5z = 0
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: November 15th 2011, 05:10 PM
  2. Normal Plane help
    Posted in the Calculus Forum
    Replies: 7
    Last Post: June 5th 2010, 01:20 PM
  3. Replies: 4
    Last Post: May 26th 2010, 10:48 AM
  4. Normal to Plane
    Posted in the Algebra Forum
    Replies: 1
    Last Post: February 10th 2010, 05:50 PM
  5. normal plane to the curve intersecting a plane
    Posted in the Calculus Forum
    Replies: 2
    Last Post: October 23rd 2009, 09:53 AM

Search Tags


/mathhelpforum @mathhelpforum