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"Work at" is a transitive verb phrase which is often translated as "trabajar en", and "work in" is a transitive verb phrase which is often translated as "incorporar". Learn more about the difference between "work at" and "work in" below.
work at( 
wuhrk
aht
)A transitive verb phrase is a phrase that combines a verb with a preposition or other particle and requires a direct object (e.g., take out the trash.).
a. trabajar en 
I've been working at the design for this company's logo all day.Llevo todo el día trabajando en el diseño del logo para una empresa.
a. poner empeño en 
With the help of her therapist, Rachel has been working at controlling her anger issues.Con la ayuda de su terapeuta, Rachel ha estado poniendo empeño en controlar sus problemas con la rabia.
b. practicar 
Daniel still needs to work at the sonata more before the audition.Daniel todavía tiene que practicar la sonata más antes de la audición.
c. darle duro 
If you keep working at it, you'll be a great gymnast.Si le sigues dando duro, serás un gran gimnasta.
work in( 
wuhrk
ihn
)A transitive verb phrase is a phrase that combines a verb with a preposition or other particle and requires a direct object (e.g., take out the trash.).
1. (to add)
a. incorporar 
Work the seasoning in so that all the meat gets that flavor.Incorpora la sazón de modo que toda la carne absorba ese sabor.
2. (to include)
a. incluir 
The band works in some of Cuban music's most famous choruses during the song.La banda incluye algunos de los coros más famosos de la música cubana durante la canción.