Question

Conic sections help

Answer 1

I get that PR+PQ=QR but how does PF+PF'=QR?

Answer 2

still there?

Answer 3

`any two tangents to a sphere drawn from a common external point have the same length`

Answer 4

for the smaller sphere,
P is the external point and PF and PQ are tangents to it.

Hence,
`PF = PQ`

makes sense?
similarly, PF' = PR

Answer 5

yes, thanks.