MathDB
Coordinate axis and prime numbers

Source: IMO LongList 1988, Hong Kong 2, Problem 26 of ILL

October 22, 2005
analytic geometrynumber theoryprime numbersgreatest common divisorgeometry unsolvedgeometry

Problem Statement

The circle x2+y2=r2x^2+ y^2 = r^2 meets the coordinate axis at A=(r,0),B=(r,0),C=(0,r)A = (r,0), B = (-r,0), C = (0,r) and D=(0,r).D = (0,-r). Let P=(u,v)P = (u,v) and Q=(u,v)Q = (-u,v) be two points on the circumference of the circle. Let NN be the point of intersection of PQPQ and the yy-axis, and MM be the foot of the perpendicular drawn from PP to the xx-axis. If r2r^2 is odd, u=pm>qn=v,u = p^m > q^n = v, where pp and qq are prime numbers and mm and nn are natural numbers, show that AM=1,BM=9,DN=8,PQ=8. |AM| = 1, |BM| = 9, |DN| = 8, |PQ| = 8.