If f (x) = x2-4x + 3, M = {(x, y) / F (x) + F (y) ≤ 0}, n = {(x, y) / F (x) - f (y) ≥ 0}, then the area of M, n is

If f (x) = x2-4x + 3, M = {(x, y) / F (x) + F (y) ≤ 0}, n = {(x, y) / F (x) - f (y) ≥ 0}, then the area of M, n is

Set M: (X-2) ^ 2 + (Y-2) ^ 2 = (Y-2) ^ 2, or (x + y-4) (X-Y) > = 0, two straight lines X + y-4 = 0 and X-Y = 0 divide m into four parts averagely, one of which is the intersection of M and N, so the area is 1 / 4 of the circle = pi / 2