Adjectives instead of adverbs

Adjectives instead of adverbs
 

Las tropas avanzaban lentas y cautelosas.
Should we not use ‘lentamente’ and ‘cautelosamente’?

Mis padres viven tranquilos.
Should we not use ‘tranquilamente’?

Many thanks in advance.

In Spanish, we avoid using the -mente ending more than once.
So, your first sentence should be "Las tropas avanzaban lenta y cautelosamente."
To describe the troops themselves, instead of describing how they marched, you could use the adjectives in question (and they would most likely precede the verb).

The second sentence is technically not correct, and should contain the adverb you mentioned. But many people use the adjective when it shouldn't be used.

I think in the last example both sentences might mean different things:

"Mis padres viven tranquilos" -> They might have had a bad experience before and now they aren't worried anymore.
"Mis padres viven tranquilamente" -> They simply have a peaceful life.



As for the troops, I agree with Rusty. It depends on what the speaker has in mind: the troops themselves or the way they move forward. :)

I was going to say that there are English-language arguments and support for both 'living happy' and 'living happily,' but many arguments against saying 'living calm'.
This is why I categorized the sentence as improper, knowing full well that it is certainly used. We English speakers certainly use 'live calm' despite the objection by some grammarians.

Thanks so much, Rusty and AngelicaDeAlquezar. Your help is very much appreciated.

@Rusty: I agree with you. I'm always torn between what I learnt as "correct" and daily speech usage. :thinking: