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Powers of  i
 
Question: How do we approach problems such as  i 1987?
 
Yours Truly answers: When  i  is raised to a large power such as  1987, we want to use  i 4 = 1.
This is because  i 4 = (i 2)2 = (–1)2 = 1. Begin by dividing the power  1987  by  4. Then,


Therefore, 1987 = 4·496 + 3. We now use some properties of exponents reviewed in Charpter  R.
 
i 1987 = i 4·496+3 = (i 4·496)(i 3) = (i 4)496(i 3) = (1)496(i 2·i ) = 1·((–1)·i ) = – i
 
 
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