I have defined three regions, `Slice1`

, `Slice2`

and `Slice3`

.

`Slice1 = Polygon[{{0, 0}, {1, 0}, {1, 1/(Sqrt[3])}, {1/2, Sqrt[3]/2}}]; Slice2 = Polygon[{{0, 0}, {-1, 0}, {-1, 1/(Sqrt[3])}, {-1/2, Sqrt[3]/2}}]; Slice3 = Polygon[{{0, 0}, {-1/2, -Sqrt[3]/2}, {0, -2/Sqrt[3]}, {1/2, -Sqrt[3]/2}}]; CombinedSlice = RegionUnion[Slice1, Slice2, Slice3]; RegionPlot[CombinedSlice, AspectRatio -> Automatic] `

When I `RegionPlot`

the combined plot, `Slice3`

does not have correct boundaries. The boundary shows up correctly when I plot `Slice3`

individually.

I am using Mathematica 12.0