A point moves so that the sum of the squares ofits distances from the ...
Let the point be (x,y,z)
Distance of this point from x = 1 is |x -1| and from x = +1 is |x + 1|. Similarly you can find the distance from the other faces. The sum of squares of distances will be,
(x - 1)^2 + (x + 1)^2 + (y - 1)^2 + (y + 1)^2 + (z - 1)^2 + (z + 1)^2 = 10
2(x^2 + y^2 + z^2 ) + 6 = 10
x^2 + y^2 + z^2 = 2
A point moves so that the sum of the squares ofits distances from the ...
Let's denote the point as P(x, y, z) and the cube as ABCDEFGH, where A = (0,0,0) is the origin and the cube has side length L.
To find the sum of the squares of the distances from P to the six faces of the cube, we can calculate the distance from P to each face individually and then square and sum those distances.
1. The distance from P to face ABCD:
Since P has coordinates (x, y, z), its x-coordinate must satisfy 0 ≤ x ≤ L. Therefore, the distance from P to face ABCD is |x - 0| = x.
2. The distance from P to face EFGH:
Since P has coordinates (x, y, z), its x-coordinate must satisfy 0 ≤ x ≤ L. Therefore, the distance from P to face EFGH is |x - L| = L - x.
3. The distance from P to face ABFE:
Since P has coordinates (x, y, z), its y-coordinate must satisfy 0 ≤ y ≤ L. Therefore, the distance from P to face ABFE is |y - 0| = y.
4. The distance from P to face DCGH:
Since P has coordinates (x, y, z), its y-coordinate must satisfy 0 ≤ y ≤ L. Therefore, the distance from P to face DCGH is |y - L| = L - y.
5. The distance from P to face AEDH:
Since P has coordinates (x, y, z), its z-coordinate must satisfy 0 ≤ z ≤ L. Therefore, the distance from P to face AEDH is |z - 0| = z.
6. The distance from P to face BFGC:
Since P has coordinates (x, y, z), its z-coordinate must satisfy 0 ≤ z ≤ L. Therefore, the distance from P to face BFGC is |z - L| = L - z.
Now, we can square and sum these distances:
x^2 + (L - x)^2 + y^2 + (L - y)^2 + z^2 + (L - z)^2
Expanding and simplifying, we get:
2x^2 + 2y^2 + 2z^2 - 2xL - 2yL - 2zL + 3L^2
Therefore, the sum of the squares of the distances from P to the six faces of the cube is 2x^2 + 2y^2 + 2z^2 - 2xL - 2yL - 2zL + 3L^2.