Let $(a,b,c)$ be the sides of a triangle inscribed inside a unit circle such that the vertices of the triangle are distributed uniformly on the circumference. Let $x$ be a real and let
$$ f(x) = P\left(\frac{1}{a-b+x} + \frac{1}{b-c+x} \ge \frac{1}{c-a+x}\right) $$
The plot of $x$ vs $f(x)$ is show below along with line $\displaystyle y = \frac{1}{2}$.
If we zoom in further, we see that the curve $y = f(x)$ intersects the half line $\displaystyle y = \frac{1}{2}$ at five points as shown below.
Experimental data show that the all the intersections occur at rational points.
Question: Is it true that $\displaystyle P\left(\frac{1}{a-b+x} + \frac{1}{b-c+x} \ge \frac{1}{c-a+x}\right) = \frac{1}{2}$ at $\displaystyle x = \pm\frac{3}{4}, \pm\frac{3}{5}$ and $0$?
Related question: Does every triangle satisfy $\frac{1}{a-b+\pi R} + \frac{1}{b-c+\pi R} - \frac{1}{c-a+\pi R} < \frac{1}{R}$?
Julia code to estimate $f(x)$:
step = 10^7
x = -4.83
while x <= 4.83
count = 0
f = 0
while count < step
count += 1
# Generate random angles for the vertices
angles = (rand(3) .* 2 * π)
# Calculate the coordinates of the vertices on the unit circle
vertices_x = cos.(angles)
vertices_y = sin.(angles)
# Close the triangle by repeating the first vertex
push!(vertices_x, vertices_x[1])
push!(vertices_y, vertices_y[1])
# Calculate the side lengths using vectorized operations
x_diff = diff(vertices_x)
y_diff = diff(vertices_y)
side_lengths = sqrt.(x_diff.^2 + y_diff.^2)
a = side_lengths[1]
c = side_lengths[2]
b = side_lengths[3]
if 1/(x+a-b) + 1/(x+b-c) > 1/(x+c-a)
f += 1
end
end
println(x, " ", f," ", string(f/count)[1:end-1], count," ")
x = round(x + 0.01, digits=3)
end

