the multiples of i
i^9 i^100 i^2017
how to answer these questions
\(i=\sqrt{-1}\)
i^1= i
i^2=-1
i^3= -i
i^4= 1
i^5= i
\(i^9 =(i^3)^3=(-i)(-i)(-i)=(-1)(-i)=i\)
\(i^{100}=((i^5)^5)^4=(i^5)^4=i^4=1\)
\(i^{2017}=(i)(i^{2016})\) ?
Excuse me. Unfortunately I do not know.
!
This is how I think of it:
For example:
i^7 = i i i i i i i
Then circle each pair of i's and replace each pair with -1.
i^7 = i i i i i i i = (i i)(i i)(i i)i = (-1)(-1)(-1)i
Then circle each pair of -1's and replace each pair with 1.
i^7 = i i i i i i i = (i i)(i i)(i i)i = (-1)(-1)(-1)i = [ (-1)(-1) ] (-1)i = [1](-1)i = -i
---------------------------------------------------------------------------
For i^2017 , we could do it the same way,
...but I don't feel like writing out all those i's!
But if I WERE to write them all out, and circle each pair of i's,
how many pairs would I get?
I would get 2017/2 = 1008 pairs of i's with a remainder of 1 i's.
Then replace every pair with a negative one and then put one i at the end.
Then if I circled each pair of negative ones, how many pairs would I get?
I would get 1008/2 = exactly 504 pairs of negative ones.
(There are no negative ones left unpaired.)
Then I would replace each pair of negative ones with a positive one.
And then I would "erase" every " 1 " that I wrote because those are not necessary to write. Whatever is left = i^2017
i^2017 = i
I hope this made sense!!