# Inside or outside the square?

Enrico draws a square in the plane, and then secretly picks a point $P$ that is either situated

• inside the square,
• or outside the square,
• or on the boundary of the square.

Damiano sees the square drawn by Enrico, but does not know the position of the secret point $P$. Damiano may choose a straight line $\ell$ in the plane and show $\ell$ to Enrico. Enrico then truthfully answers Damiano whether the secret point $P$ lies on line $\ell$, and in case the point is not the line, on which side of $\ell$ this secret point is located.

Question: What is the smallest possible number of lines that Damiano can query so that he will discover with absolute certainty whether the secret point is inside, outside, or on the square?

• After my first rash answer, I think there is no answer. It doesn't matter where Enrico puts the point. Damiano would need to do something like binary search to find the $X$ and $Y$ coordinates. If $P$ has irrational coordinates, then $P$ will never be found for any $N$. – Trenin Oct 20 '15 at 16:58
• Are we trying to find the coordinates to $P$, or whether it's inside or outside the square? – JonTheMon Oct 20 '15 at 16:59
• @JonTheMon Must be trying to find if $P$ is inside or outside the square. – Trenin Oct 20 '15 at 17:18
• What the heck does the square have to do with anything? – user2357112 supports Monica Oct 20 '15 at 22:50