Question 1093964
i^7
(i^3)^2 x i
-i x -i = i
i x i = i 
i^49 
i^99 
i^91 
i^473 
i^2001 
i^8 + i^9 + i^10 
-----------------------
i^1 = i
i^2 = -1
i^3 = -i
i^4 = 1
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It's "modulus 4" of a sort
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i^7 = i^4*i^3 = i^3
= i^2*i = -i
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(i^3)^2 x i
-i x -i = i
i x i = i 
---
i^49 
= i^48*i = i
===============
i^99 
= i^96*i^3 = -i
===============
i^91 
i^473 
i^2001 
i^8 + i^9 + i^10
= 1 + i - 1
= i