Find the locus of the centre of a variable sphere which passes through...
The locus of the center of a sphere that passes through the origin and meets the axes in points A, B, and C is a plane. To find this plane, we can use the equation for the volume of a tetrahedron:
V = (1/3) * A * h
where V is the volume of the tetrahedron, A is the area of the base, and h is the height from the base to the opposite vertex (in this case, the origin).
Since the volume of the tetrahedron is constant, the value of h will also be constant. The height of the tetrahedron is the distance from the plane containing the base to the opposite vertex (the origin). This distance can be found using the equation:
h = (D/n)
where D is the distance from the origin to the plane containing the base, and n is the normal vector of the plane.
To find the equation of the plane containing the base, we can use the coordinates of the points A, B, and C. Let's assume that the coordinates of A, B, and C are (a, 0, 0), (0, b, 0), and (0, 0, c), respectively. The normal vector of the plane can be found using the cross product of two vectors in the plane:
n = (b - 0, 0 - 0, 0 - 0) x (0 - 0, c - 0, 0 - 0)
= (0, 0, b) x (0, c, 0)
= (bc, 0, -ac)
The equation of the plane containing the base is then:
D = n . O
where O is the position vector of the origin.
Substituting the values we have calculated, we get:
D = (bc, 0, -ac) . (0, 0, 0)
= 0
Therefore, the equation of the plane containing the base is:
0 = bcx + 0y - acz
This is the equation of the plane that is the locus of the center of the sphere that passes through the origin and meets the axes in points A, B, and C, and has a constant volume tetrahedron of OABC.