Poor English.
like - use with nouns, adjectives.
as if - use with verbs, clauses
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"You seem as if you are down in a trough."
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A "trough" is a depression, a low. Terrain, in numbers, figures, weather atmospheric pressure. Can be used litterally, figuratively.
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Also a low, container, without a top, used for feeding animals, among other things.
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Depends on your context, but as a question here, most likely figuratively, meaning a moitavtion low.
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Seems you are down in a trough. Maybe get out more? Go see a movie with friends.
"down in" sort of suggests this.
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Your weather there is terrible at the moment. Seems you are in a pressure trough, behind that cold front moving across the country.
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I can't see you above the heather, are you standing down in a trough of some sort? Are you down some small valley, or something?
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Put the carrots in the trough for the animals.