Mathematics
Grade 11
15 min
Powers of i
Powers of i
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Introduction & Learning Objectives
Learning Objectives
Define the imaginary unit `i` and its fundamental powers (`i^0`, `i^1`, `i^2`, `i^3`).
Identify the cyclical 4-step pattern of the powers of `i`.
Develop and apply a method to simplify `i^n` for any non-negative integer `n`.
Simplify expressions involving negative integer powers of `i`, such as `i^-n`.
Evaluate sums and products of expressions involving various powers of `i`.
Apply the properties of exponents to simplify complex expressions with powers of `i`.
What happens when you keep multiplying a number by itself, but the result repeats every four steps? 🤔 Let's explore the strange and wonderful world of the imaginary unit `i`!
This tutorial will demystify the powers of the imaginary unit, `i`. You will learn to recognize their repeating, cycli...
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Key Concepts & Vocabulary
TermDefinitionExample
Imaginary Unit (i)The fundamental imaginary unit, defined as the principal square root of -1. It is the basis of complex numbers.`i = \sqrt{-1}`, which means `i^2 = -1`.
Complex NumberA number of the form `a + bi`, where `a` and `b` are real numbers and `i` is the imaginary unit. `a` is the real part and `bi` is the imaginary part.`3 + 4i` is a complex number.
PowerThe result of repeatedly multiplying a number (the base) by itself. The number of times it is multiplied is the exponent.In `i^4`, `i` is the base, `4` is the exponent, and the expression means `i \cdot i \cdot i \cdot i`.
Cyclical PatternA sequence of values that repeats in a predictable, fixed order. The powers of `i` follow a cycle of four distinct values.The sequence of values for `i^1, i^2, i^3, i^4,...
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Core Formulas
The Fundamental Cycle
`i^0 = 1`
`i^1 = i`
`i^2 = -1`
`i^3 = -i`
These are the four fundamental powers of `i` that form the basis of the repeating cycle. All other integer powers of `i` will simplify to one of these four values.
The Simplification Rule for i^n
`i^n = i^r`, where `r` is the remainder of `n \div 4`.
To simplify `i` to any non-negative integer power `n`, divide `n` by 4 and find the remainder `r`. The value of `i^n` is the same as `i^r`. The remainder `r` will always be 0, 1, 2, or 3.
The Rule for Negative Exponents
`i^{-n} = \frac{1}{i^n}`
To simplify `i` to a negative power, first rewrite it as a fraction using the rule of negative exponents. Then, simplify the denominator `i^n` and rationalize if necessary.
5 more steps in this tutorial
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Challenging
What is the sum of the first four consecutive powers of `i`, starting from `i^1`? (i.e., `i^1 + i^2 + i^3 + i^4`)
A.0
B.1
C.4i
D.-1
Challenging
Using the pattern that the sum of any four consecutive powers of `i` is 0, what is the value of the sum `i^1 + i^2 + i^3 + ... + i^{100}`?
A.0
B.1
C.i
D.100
Challenging
If `n` is any positive integer, the expression `i^{4n+3}` will always simplify to:
A.i
B.-1
C.1
D.-i
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