Assertion : Two spheres of radii `r_1` and `r_2` cut orthogonally, then radius of the common circle is `(r_1r_2)/(sqrt (r_(1)^2 + r-(2)^2) )`

Reason : If two spheres `x^2 + y^2 + z^2 + 2ux + 2vy + 2wz + d = 0` and `x^2 + y^2 + z^2 + 2u' x + 2v' y + 2w' z + d' = 0` cuts orthogonally, then `2u u' + 2v v'+ 2w w' = d + d' `