Short answer: a confusing something and a confused something are similar, and closely related, but not necessarily the same.
Let's try a simpler verb: interesting--interested. There are 3 people in this example, A, B, and C. Suppose that,
A interests B. -- Let's say that A successfully gets B's attention by making himself or herself look interesting. We can say that, B finds A interesting.
C may observe that,
- A is an interesting person (to B), and
- B is the interested person.
C may or may not think that B is interesting. However, if C thinks that the fact that B is interested in A makes B interesting, C may think that B is interesting, too, which in turn makes C think that,
- B is the interested person, and
- B is an interesting person.
In this case (to C), B is both interesting and interested.
The same applies to confusing and confused in your question.
When we say or write confusing ideas, we mean that to us, the ideas are confusing, and we look at it from our point of view. We feel that they are "confusing". To us, it's difficult to understand.
When we say or write confused ideas, we mean that the ideas are confused. They are not well organized or explained. We may say that the person who states the ideas "confuse" them, and as a result, the ideas are not clear or not easy to understand.
Thus, a confusing something may not be confused.
And a confused something may not be confusing, either.
In short, they're similar, and closely related, but not necessarily the same.
It seems as if there really should be some common adjective to describe engineering things -- but, unlike so many other disciplines, there isn't. "Engineerical" is not a word, or at least not one you would use seriously.
There are several solutions to this deficit:
(As per Lambie's suggestion) rewrite the sentence using nouns:
The questions on the exam can be about physics, math, history, or engineering
Use a semantically correct but stylistically awkward compound:
The questions on the test can be physical, mathematical, historical, or engineering-related
Use an awkward repeating term that nevertheless preserves parallelism:
The questions on the test can be physics-related, math-related, history-related, or engineering-related
Note that the use of "physical" to mean "physics-related" may be confusing, as the more common uses are:
physical (adj):
1 Relating to the body as opposed to the mind.
1.1 Involving bodily contact or activity.
2 Relating to things perceived through the senses as opposed to the mind; tangible or concrete.
Best Answer
The meaning of subsequent is simply "following" or "coming after", as you discovered, but it does not necessarily mean immediately or directly following.
Here are some examples that show how the word is used:
Here, "subsequent" means "coming later", but it obviously doesn't mean "right after dropping out of high school".
Obviously, all of the twelve proceedings were subsequent to the first.
So yes, I would say that 3 is subsequent to 1 in your example, although to make things completely clear, I might say that it's one of the subsequent things.
If you want to specify "the very next one", I would suggest that the best term to use is immediately subsequent (although directly subsequent is pretty good too). For example,
Here "immediately subsequent" means "the very next month".
Again, "immediately subsequent to" means "right after".
You can say that 2 is immediately subsequent to 1, but I wouldn't say that 1 and 2 "are immediately subsequent", because one of them is subsequent to the other, saying "1 and 2 are immediately subsequent" makes it sound like they both come after something else.