If (mi,1mi), i = 1, 2, 3, 4 are con - cyclic points, then the value of m1m2m3m4 is
1
Let equation of circle be x2+y2 + 2gx + 2fy + c = 0. If (m,1m) lies on this circle, then
m2+1m2+2gm+2f1m+c=0
or m4+2gm3+2fm+cm2+1=0
This is a fourth degree equation in m having m1,m2,m3,m4 as its roots.
Therefore, m1m2m3m4 = product of roots = 11 = 1.