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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
- santmann2002Lv 710 years agoFavorite 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
- DambarudharLv 710 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 = â(1² + 3² + 2²) = â14
Unit Vector in the direction OA = (1 / â14)(i + 3 j - 2 k)
Since OA is perpendicular to the the plane, then the unit vector normal to the plane is
( n ) = (1 / â14)(i + 3 j - 2 k)
Now the projection of OP on OA = ( OP ) â ( n ) = (6 i + j - 2 k) â {(1 / â14)(i + 3 j - 2 k)}
= (1 / â14) ( 6 + 3 + 4) = (13 / â14) = Length of the perpendicular from the origin on the plane
Hence the vector equation of the plane is ( r ) â ( n) = (13 / â14)
For the cartesian equation : Put ( r ) = x i + y j + z k and ( n ) = (1 / â14)(i + 3 j - 2 k)
and you get x + 3y - 2z = 13
- ?Lv 710 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