Solving an Odd Function with Periodicity

[billy1024]

Homework Statement

Basically, I had a test yesterday and one of the questions was:

"an odd function f(x) has a period τ=7. What is the value of f(75)-f(-30)"

Homework Equations

n/a

The Attempt at a Solution

I used periodicity to reduce

= f(75-70) + f(30-28)
= f(5) + f(2)

What else could I have done?

 

[tiny-tim]

welcome to pf!

hi billy1024! welcome to pf!

I used periodicity to reduce

= f(75-70) + f(30-28)
= f(5) + f(2)

What else could I have done?

hint: what is the relation between f(5) and f(2) ?

 

[Deveno]

since f is odd, f(-2) = -f(2), so f(2) = -f(-2).

what is 5 - (-2)?