1. He is A teacher and A dancer.
2. He is A teacher and dancer.

Are they correct?

Thanks in advance!

Question

1. He is A teacher and A dancer.
2. He is A teacher and dancer.

Are they correct?

Thanks in advance!

Answer

2

To avoid the cofusion just memorize the following example:
The bank was robbed by a teacher and dancer <= one robber.
The bank was robbed by a teacher and a dancer

Answer

1 is more common. 
2 is less common but understood by everyone. I do not think it is ambiguous.
You may be aware of the "distribution law of multiplication" from 5th grade: 
      n(a + b) = na + nb.   Example: 5(2 + 3) = 5(2) + 5(3) = 25
The 5 is distributed over the terms.
Like your A is distributed over the nouns.
Same same: He is a great teacher and dancer. Means he is great at both.
This can be emphasized with "both", therefore:
3: He is both A teacher and dancer.

Answer

The first 1 is correct. If you say either, no one will correct you, and I imagine that plenty of native speakers will say the second one not knowing they aren't saying it right.

لا تفوّت فرصة تعلّم لغة جديدة وأنت مرتاح في منزلك. تصفّح مجموعتنا المختارة من مدرّسي اللغات ذوي الخبرة وسجّل في درسك الأول الآن!