Prove that `A subset phi => A=phi`

For any set A, prove that A sube phi hArr A =phi .

Prove that A sub phi implies A =phi .

{phi} = phi

Prove that : phi- A= phi .

Prove that for a null set phi, n{P(P(phi))}=2 .

If sqrt(a + b) tan = theta/2 = sqrt(a -b) tan phi/2 then prove that a + b cos phi = (a cos phi+ b) sec theta .

Prove that : A nn(B-A)=phi .

Prove that A cap (A cup B)'=phi .

If A and B are two events such that P(A) ne 0 and P(B | A)=1 , then a) A subset B b) B subset A c) B=phi d) A=phi