in an adjective phrase

Question

In a English dictionary, I run across a sentence I can't grasp.

1. I sat down deep in contemplation.

Can I change the sentence into the following.

2. I sat down and I was deep in contemplation.

Does the both have the same meaning? If not, what difference there is?

and can I say that the phrase(deep in contemplation) is an adjective phrase and a complement of the subject

Answer 1

Yes, deep in contemplation describes I, the subject.

I think I would put 2 as
I was deep in contemplation, and I sat down.
That just seems a more natural order of events: the contemplation was an existing state, and the sitting down occurred while I was in that state.