Problem 86 - Precalculus Student Solutions Manual 5th

Question

Simplify each power of i. $$i^{29}$$

Step-by-Step Solution

Answer

i^{29} = i

Step 1: Understand the Powers of i

Know the cyclic nature of the imaginary unit, i. The powers of i repeat every 4 terms: i^1 = i i^2 = -1 i^3 = -i i^4 = 1Thus, any power of i can be reduced to one of these four values.

Step 2: Express the Exponent Modulo 4

To simplify the power i^{29}, find the remainder when 29 is divided by 4. 29 ÷ 4 gives a quotient of 7 and a remainder of 1. Therefore, 29 ≡ 1 (mod 4).

Step 3: Simplify the Expression

Since 29 ≡ 1 (mod 4), we can write: i^{29} = i^1 = i.

Key Concepts

imaginary unit

Imaginary numbers are numbers that include the imaginary unit, denoted by 'i'. The imaginary unit is defined by the property that when squared, it equals defined as: i^2 = -1.
.This can be surprising because we are used to dealing with numbers that produce positive results when squared, but imaginary numbers provide a way to work with square roots of negative quantities.
.In mathematical terms, the imaginary unit helps us extend the real number system to the complex number system.
.Imaginary numbers, along with real numbers, make up complex numbers, which are in the form a + bi, where 'a' and 'b' are real numbers.
.For example, 3 + 4i is a complex number where 3 is the real part and 4i is the imaginary part.
.Understanding the imaginary unit is crucial for simplifying powers of i. Let's explore how this works in a cycle.

cyclic nature

Powers of i follow a repeating pattern, known as its cyclic nature. This cyclic nature is crucial for simplifying higher powers of i.
.The pattern is:

• i^1 = i
• i^2 = -1
• i^3 = -i
• i^4 = 1

Beyond i^4, the pattern repeats itself:

• i^5 = i
• i^6 = -1
• i^7 = -i
• i^8 = 1

This cycle runs every four powers. Thus, any power of i will be equivalent to one of these four options: i, -1, -i, or 1.
.Understanding this cyclic nature will allow us to simplify expressions like i^29 effortlessly by identifying their equivalent lower powers.
.Next, let's use modular arithmetic to tie everything together.

modular arithmetic

Modular arithmetic is a system of arithmetic for integers, where numbers wrap around upon reaching a certain value—like hours on a clock.
.It is often denoted with 'mod' notation.
.To simplify i^29, we use modular arithmetic to find the remainder when 29 is divided by 4. This process is called finding the modulus.
.To do this:

29 ÷ 4 = 7 remainder 1, or in modular arithmetic form, 29 ≡ 1 (mod 4).

This tells us that 29 is equivalent to 1 in terms of powers of i. Therefore, i^29 is equivalent to i^1 which equals i.
.Using modular arithmetic in conjunction with the cyclic nature of i makes simplifying powers of i much easier.
.Remember, these concepts help break down seemingly complex calculations into simpler steps that are easy to manage.