Theorem (proof that) a) A Delta B = AÚ B if A Subscription B

[reza95]

Theorem (proof that)
a) A Delta B = AÚ B if A Subscription B= Null
b) A Subscription (B Ù C) = (A Subscription B) Ù (A Subscription C)

sorry for bad typing , I got error. better form : http://mathhelpforum.com/discrete-math/226661-theorem-proof.html#post812654
please help me.
thank you.

[stapel_eliz]

Theorem (proof that)
a) A Delta B = AÚ B if A Subscription B= Null
b) A Subscription (B Ù C) = (A Subscription B) Ù (A Subscription C)

What does "Delta" indicate? What does "Ú" mean? What does "Subscription" mean in this context? Does "Null" mean "the empty set"?

What are your thoughts? What have you tried? How far did you get? Where are you stuck?

Please be complete. Thank you!

[reza95]

I am so sorry , when I want right I get Error and can not submit my post.

Please visit : http://mathhelpforum.com/discrete-math/226661-theorem-proof.html
I writing right there.
thank you.

[stapel_eliz]

Okay; what does "" mean? What does "Ú" mean? Does "" mean "the empty set"?

Seriously: You have to tell people what you mean. And, before anybody can help you get un-stuck, you have to show what you've tried so far.

Please be complete. Thank you.