Suppose that R is a relation of set A. If for any a, b, c∈A satisfying (a, b)∈R, (b, c)∈R, it follows that (a, c)∈R, then relation R has ______ .
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Suppose that R is a relation of set A. If for any a, b∈A satisfying (a, b)∈R, it follows that (b, a)∈R, then the relation R has ______ .
Suppose that R is a relation of set A. If (a, a)∈R for any a∈A, then relation R has ______ .
Let ∘ be a binary operation on set A. If there exists e∈A such that for any x∈A ,it holds that e∘x=x∘e=x, then e is called of operation ∘ ______ .
The ______ of the square inscribed in a circle whose radius is R is 2R2.