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# C3 - Domain and range Watch

1. I'm confused about this. When asked to find the greatest possible domain of, for example, root(x), my college handout says x is a member of R and x is >= 0. But why is this? Isn't the greatest possible domain x is a member of C unless it is stated that the codomain is real?
2. (Original post by GeneralOJB)
I'm confused about this. When asked to find the greatest possible domain of, for example, root(x), my college handout says x is a member of R and x is >= 0. But why is this? Isn't the greatest possible domain x is a member of C unless it is stated that the codomain is real?
Consider the fact that a well-defined function maps every input to a unique output. Note that the converse is false.

Darren
3. (Original post by GeneralOJB)
I'm confused about this. When asked to find the greatest possible domain of, for example, root(x), my college handout says x is a member of R and x is >= 0. But why is this? Isn't the greatest possible domain x is a member of C unless it is stated that the codomain is real?
If you're studying this as part of C3 then the general assumption is going to be that all the functions you encounter take real arguments and produce real results.

Unfortunately complex numbers seem to have been moved out of A level and into the FM syllabus as far as I can see

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Updated: April 13, 2013
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