MathDB
Putnam 1981 B6

Source: Putnam 1981

March 31, 2022
PutnamintegrationcalculusDouble integral

Problem Statement

Let CC be a fixed unit circle in the cartesian plane. For any convex polygon PP , each of whose sides is tangent to CC, let N(P,h,k)N( P, h, k) be the number of points common to PP and the unit circle with center at (h,k).(h, k). Let H(P)H(P) be the region of all points (x,y)(x, y) for which N(P,x,y)1N(P, x, y) \geq 1 and F(P)F(P) be the area of H(P).H(P). Find the smallest number uu with 1F(P)N(P,x,y)  dx  dy<u \frac{1}{F(P)} \int \int N(P,x,y)\;dx \;dy <u for all polygons PP, where the double integral is taken over H(P).H(P).