# Re: The seven step-Mathematical preliminaries 2

```  Bruno,
When I tried to copy the symbols from the URL cited below, I
found that my email server was not able to reproproduce the intersection or the
union symbol. See below:```
```
From: Bruno Marchal

∅ ∪ A = I see two rectangles and  "A"
∅ ∪ B = I see two rectangles and "B"
A ∪ ∅ = I see "A" and two rectangles
B ∪ ∅ = I see "B" and two rectangles
N ∩ ∅ = I see "N"  Inverted "U"  and a rectangle
B ∩ ∅ = I see "B"  Inverted "U"  and a rectangle
∅ ∩ B = I see a rectangle  an inverted "U"  and "B"
∅ ∩ ∅ = I see a rectangle  an inverted "U"  and a rectangle
∅ ∪ ∅ = I see three rectangles
----- Original Message -----
From: Bruno Marchal

You could look on the archive, from here,

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