Technically, Я устала = "I got tired", and "I am tired" = Я уставшая, but no one talks like that, so you have to use "Я устала" here too. And since Russian doesn't have a "Past Perfect" tense, "I was tired" is also translated as Я устала.
It just doesn't sound like proper Russian.
Everyone would say "Я устала" in all cases.
Hm, I suppose you're right.
However we can't use уставшая in all cases. For example, a person who is tired would rather say "Я устал!" than "Я уставший!" Especially when the word is alone (without такая etc). So I think it is easier for the Russian learners to memorize only one but flexible and always appropriate way to express it.
уставшая is a participle, maybe that's why people don't prefer it here; participles are more common in written and/or formal Russian, not so much in conversation (though there are exceptions like следующий 'next' or бывший 'former'). I have a few videos about them here (http://preview.tinyurl.com/z3obl53), but people who are just starting out with Russian shouldn't worry about them too much at the beginning.
I've got a surprise for you: уставшая is NOT a participle in such context
Thanks. I'm not native, so I get some of these things wrong... I was thinking on sentences like "I've got to go" and "I've got something for you".
If "Я устал" means "I AM tired", then how do you say "I WAS tired"? "Я был усталым"?
I suppose, "I was tired" requires some additional past time indicator. For example, "I was tired yesterday" would be OK, but it means "Я была уставшей вчера". "Я устала" without any time indicator suggests that I got tired and I am tired in the present moment.
It can be used in all cases. i am tired, I was tired. It's the same but only that word
It's funny how they say it as a girl version of the word, but they used a man's voice in the actual question in a lesson.
Почему ответ "я устал" засчитан как неправильный? Правильным считается только: "Я усталА". "I am tired". Где здесь половые признаки?