mere 和 trivial 的差別在哪裡？如果不好說明，請提供一些例句。

This is a really hard question.
The difference is very subtle. Both are adjectives, but they are used in different ways.
Trivial means a thing of little or no importance and is categorical. Something that is trivial is very commonplace or can be ignored.
Mere is a comparative. Something that is called mere is only mere in comparison to something greater.
In some cases the two words are interchangeable, but not always.

"Joe was a mere delivery boy." -- suggests that within his employer's organization, Joe was low-ranking, but might be promoted to a better position." It's a criticism.
"Joe was a trivial delivery boy." -- suggests that Joe was unimportant because all delivery boys are unimportant. It's a condemnation.
The second example can also be read to suggest that, among delivery boys generally, Joe is a particularly unimportant one.

"It was a mere paragraph." -- suggests that the topic might have deserved a longer essay, or that the reader might have expected more information, but the author only wrote a single paragraph about it.
"It was a trivial paragraph." -- suggests that among all the other paragraphs in an article, this one paragraph said little of significance.

"It was a mere mistake." -- implies that it was only a mistake, not a malicious act.
"It was a trivial mistake." -- implies that as mistakes go, it was not a disastrous mistake. It was a small or unimportant mistake.

For mere, you can usually substitute "just," "only," "but," or "simply."
"It was only a mistake." "It was but a mistake." "It was simply a mistake." "It was just a mistake."

Trivial has a noun form, trivia. Trivia are unimportant or insignificant things.
You can say that "People's opinions about hairstyles and TV shows are trivia." but you can't do the same thing with the word "mere."
However, you can say that "People's opinions about hairstyles and TV shows are mere trivia." But then, you can't say that "People's opinions are trivially mere."

The adverb forms, "merely" and "trivially," also differ in use.
One could say, "I merely asked a question," implying that I did nothing extraordinary.
One would not say "I trivially asked a question."

I'll look into this some more and get back to you.