I'm in a calc I class where I'm faced with the question:
Suppose that f(x) is an odd function, and periodic with period 10. If f(3) = 4, find f(7) + f(5).
Unfortunately, this is not talked about in our text, which says to me I already have this knowledge but can't seem to make sense of it.
I know that an odd function has the property f(-x) = –f(x), but how does that help if I don't know f(x)?
What I was able to find thus far has been tied to more complex ideas which I don't know and we have yet to cover. It said a function is periodic if f(x + T) = f(x). Is this going in the right direction, and if so how can go about dumbing it down a tad?
Any links to info, hints towards a direction, an explanation of the type of problem this is would be appreciated.
Best Answer
Hint: You correctly translated "odd function". You know $f(3)$, so you know $f(-3)$ and similarly for any couple of opposite values of the argument of $f$.
Now, $f$ is periodic of period $10$, so $f(3)=f(3-10)=f(-7)$. But then...