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Im trying to study abstract algebra, set theory and group theory, on my own. I have trouble understanding how to construct mathematical proofs though. Some of the things the excercises tells me to prove, seems so intuitively clear and obvious that I don't know what's left to prove. For example, prove that

[tex]

A\cup B = B\cup A

[/tex]

where A and B are two sets, or

[tex]

A\cap(B\cup C)=(A\cap B)\cup (A\cap C)

[/tex]

I have no idea how to start. Can someone give me a hint on these? And maybe a hint on general proof making in mathematics?

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# Proofs in mathematics

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