A circle of radius 2 is contained in the plane y=3.
A circle of radius 4 is contained in the plane y=7.
Both circles lie on the surface of a sphere.
What is the radius of the sphere?
(In reply to
No Subject by bernie)
Let one of the unknown legs be x, and the other (4x). Then
r^2 = 2^2 + (4x)^2 = 4^2 + x^2
Forgetting r for the moment, and expanding:
20  8x + x^2 = 16 + x^2
Solving:
x=1/2
Substituting:
r^2 = 16 + 1/4
r=sqrt(16.25) or about 4.031128874149275.

Posted by Charlie
on 20040826 14:32:20 