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Real part
From OeisWiki
ℜ (z) 
z = r e i θ = r cos θ + i r sin θ = a + i b = ℜ (z) + i ℑ (z) 

ℜ (z) := a =
= r cos θ,z + z̅ 2
z̅ 
z 
For example,
ℜ (3 + √ − 5 ) = 3 
The real part of a zero of the Riemann zeta function is either an even negative integer (for trivial zeros) or

Compare imaginary part.