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Simplify i raised to the power 27. What is the result?
ANegative i
BPositive i
CNegative one
DPositive one
Answer & Solution
Correct answer: A. Negative i
1. The powers of i repeat in a cycle of length 4, running i, negative 1, negative i, then 1.
2. So a power of i depends only on the remainder when the exponent is divided by 4.
3. Divide 27 by 4 to get 6 with a remainder of 3.
4. That means i to the 27 equals i to the 3.
5. The third entry of the cycle is negative i, so the answer is negative i.
6. Answering positive i would use a remainder of 1, which comes from dividing 25 rather than 27.
7. Answering negative one would use a remainder of 2.
8. Answering positive one would use a remainder of 0, which happens only for multiples of 4.
_Source: OpenStax Precalculus (CC BY 4.0), section 3.1 Complex Numbers_
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