MathDB

3

Part of 1990 IMO Longlists

Problems(1)

Prove that S(ABC) is no larger than 9/2

Source:

9/19/2010
In coordinate plane, we call a point (x,y)(x, y) "lattice point" if both xx and yy are integers. Knowing that the vertices of triangle ABCABC are all lattice points, and there exists exactly one lattice point interior to triangle ABCABC (there might exist lattice points on the sides of ABCABC). Prove that the area of triangle ABCABC is no larger than 92.\frac 92.
analytic geometrygeometry