Solution
= Solution
The centre-to-plane distance is $|g-2|/\sqrt2$. Intersection occurs iff this is at most $2\sqrt2$, i.e. $-2\le g\le6$. Equality gives one tangent point; strict inequality gives a circle of radius $\sqrt{8-(g-2)^2/2}$.
= Solution
The centre-to-plane distance is $|g-2|/\sqrt2$. Intersection occurs iff this is at most $2\sqrt2$, i.e. $-2\le g\le6$. Equality gives one tangent point; strict inequality gives a circle of radius $\sqrt{8-(g-2)^2/2}$.