Hello,

I want to know how the following formula in logic is called:

Remarks:

(1) I once read in a book ("Theory and Problems of Logic", McGraw-Hill) calling it "the absorption law".

(2) In many textbooks, I see:

"the absorption law"----

"the idempotent law"----

(3) The formula in question is often found in set theory in the form:

Thank you for your time...