Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.

Could somebody solve this vector problem please?

Find the vector and cartesian equations of the plane which passes through (6, 1, -2) and is perpendicular to the vector (1, 3, -2).

I'm totally lost here and have no idea where to start. I know that the scalar product is zero, so I got x+3y-2z=0. But I don't know what this means, or how it helps me to solve the problem. Please help.

3 Answers

Relevance
  • 10 years ago
    Favorite Answer

    the equation of the plane is x+3y-2z+d=0 and as it passes through (6,1,-2)

    6+3+4+d=0 so d=-13 and the plane is x+3y-2z-13=0

  • 10 years ago

    Let P be the point P ( 6, 1, -2) and O be the origin O (0, 0, 0)

    Vector ( OP ) = 6 i + j - 2 k , where i, j, and k are the unit vectors in the directions of the

    x, y and z axes respectively

    Similarly, if A is a point A (1, 3, - 2) , then Vector ( OA ) = i + 3j - 2 k

    The length of the Vector OA = √(1² + 3² + 2²) = √14

    Unit Vector in the direction OA = (1 / √14)(i + 3 j - 2 k)

    Since OA is perpendicular to the the plane, then the unit vector normal to the plane is

    ( n ) = (1 / √14)(i + 3 j - 2 k)

    Now the projection of OP on OA = ( OP ) ∙ ( n ) = (6 i + j - 2 k) ∙ {(1 / √14)(i + 3 j - 2 k)}

    = (1 / √14) ( 6 + 3 + 4) = (13 / √14) = Length of the perpendicular from the origin on the plane

    Hence the vector equation of the plane is ( r ) ∙ ( n) = (13 / √14)

    For the cartesian equation : Put ( r ) = x i + y j + z k and ( n ) = (1 / √14)(i + 3 j - 2 k)

    and you get x + 3y - 2z = 13

  • ?
    Lv 7
    10 years ago

    A plane is a locus .- All vectors in the space that are normal to a given direction .-

    If R (x,y,z( is a position vector of the plane ( It is a point on the plane ) , ie

    R= x i+yj+zk and passes by a other position vector like P = ai+bj+zk now , A VECTOR on the plane is V= R-P .- This vector must be normal to a given direction , N , so

    V dot N =0

    (R-P) dot N=0 This is the vectorial equation of a plane .-

    This is ,

    ((x-a) i+(y-b)j+(z-c) k) dot( Nxi+Nyj+Nzk) =0

    Nx(x-a)+Ny(y-b)+Nz(z-c)=0

    Nx x +Ny y +Nz z - (Nxa+Nyb+Nzc) =0

    - (Nxa+Nyb+Nzc)= a cosnstant = D so finally

    Nx x+Ny y+Nz z +D =0

    is the cartesian eq of a plane .-

    Is very important that you note that given a cartesian equation of the plane , the factors of x, y, z are the Normal components of the plane , ie its NORMAL vector .-

    In your case , passes by (6,1,-2) , so a vector on the plane is R-(6,1,-2) and is Normal to N(1,3,-2) .- So all is given .-

    The plane is (x-6) i +(y-1) j + (z+2) k dot (1,3,-2)=0

    /x-6) +3(y-1)-2( z+2)=0

    x+3y-2z -13=0

Still have questions? Get your answers by asking now.