Hi all. I can't remember what this type of function is called for the life of me, so sorry for being vague in the description. This is just part of a much bigger question and for some reason I get stuck at this part...

I have two functions:

f(t) = 1 for 0 < t < 1 and -1 for 1<t<2

f(t-T) = 1 for 0 < t-T < 1 and -1 for 1<t-T<2

so far so good.

I'm supposed to know that f(t) = f(t-T) = 1 for 0<t<1-T, but how do I know this? I've not done a problem like this in like 3 years, so please give me some pointers.