# Plot a two-set Venn diagram with proportional discs and intersection

Is it possible to plot a two-set/disc Venn diagram with proportional discs and intersection without having to use the below "trial-and-error" code? In the example below the left disc has 6 elements (disc area = 6), the right disc has 4 elements (disc area = 4) and the intersection has 2 elements (area = 2)

a1 = 6;
a2 = 4;
a1capa2 = 2;
d = 1.21;
y1[x_] := Sqrt[a1/π - x^2]
y2[x_] := Sqrt[a2/π - (x - d)^2]
Plot[
{y1[x], -y1[x], y2[x], -y2[x]}, {x, -2, 4},
AspectRatio -> Automatic, PlotStyle -> {Black}
]
x0 = x /. Solve[y1[x] == y2[x], x][]
caparea = 2 (N[Integrate[y2[x], {x, d - Sqrt[a2/π], x0}]] +
N[Integrate[y1[x], {x, x0, Sqrt[a1/π]}]]
)


Here I have to guess the distance $$d$$ between the discs in order to get the intersection area, caparea, to the requested 2. (It also give an imaginary reply, which I find odd.) I'm looking for a solution where you only input the disc areas, and the intersection area and the distance $$d$$ is calculated and the graph plotted.

There are several other solutions for Venn diagrams but they all seem to have the same disc size.

TIA.

You could use Region functionality instead. Your disks:

d1 = Disk[{0,0}, Sqrt[6/π]];
d2 = Disk[{d,0}, Sqrt[4/π]];


The intersection area:

area = Assuming[1 < d < 2, Area @ RegionIntersection[d1, d2]];
area //TeXForm


$$\frac{-8 \sin ^{-1}\left(\frac{\pi d^2-2}{4 \sqrt{\pi } d}\right)+12 \sec ^{-1}\left(\frac{2 \sqrt{6 \pi } d}{\pi d^2+2}\right)-\sqrt{-\pi ^2 d^4+20 \pi d^2-4}+4 \pi }{2 \pi }$$

Solving to find d:

sol = d /. First @ NSolve[area == 2 && 1 < d < 2, d]


1.21455

Visualization:

Block[{d = sol},
Graphics[{FaceForm[None], EdgeForm[Black], d1, d2}, Axes->True]
] 