Problem 96 - Precalculus Student Solutions Manual 5th

Question

Simplify each power of i. $$\frac{1}{i^{-12}}$$

Step-by-Step Solution

Answer

1

Step 1: Understand the Powers of i

Recall that the imaginary unit i follows a cyclic pattern: \(i^1 = i\), \(i^2 = -1\), \(i^3 = -i\), \(i^4 = 1\). This cycle repeats every four powers.

Step 2: Simplify the Exponent

Simplify the exponent by noting that \(i^{-12}\) can be rewritten using the cycle of 4: \(i^{-12} = (i^4)^{-3} = 1^{-3} = 1\).

Step 3: Substitute Back into the Expression

Replace \(i^{-12}\) with 1: \[ \frac{1}{i^{-12}} = \frac{1}{1} = 1 \]

Key Concepts

imaginary unit

The imaginary unit, denoted as i, is a fundamental concept in complex numbers. It is defined as the square root of -1. Mathematically, this means: \(i = \sqrt{-1}\). Because the square root of -1 cannot be represented using real numbers, we use the imaginary unit i to extend the real number system into the complex number system. This extension allows for the solution of equations that do not have real solutions, such as \(x^2 + 1 = 0\). In this equation, \(x = i\) or \(x = -i\). \Breaking down the imaginary number property leads to the cyclic pattern of i, which is very useful in simplifying expressions involving powers of i. It's vital to understand its behavior to maneuver through complex equations efficiently.

cyclic pattern of i

The powers of the imaginary unit i follow a repeating cycle. Understanding this cyclic pattern helps simplify complex expressions quickly. Here’s how the cycle works: \ \[i^1 = i\, \i^2 = -1\, \i^3 = -i\, \i^4 = 1\.\] \Every power of i can be expressed in terms of \i, i^2, i^3,\ or \i^4\, and the cycle repeats every four exponents: \[i^5 = i^1\, \i^6 = i^2,\ \i^7 = i^3,\ \i^8 = i^4\]. This repeating pattern is crucial for simplifying higher powers of i, as we can reduce the exponent to within the range of 1 to 4. For example, \i^{-12}\ can be handled by this cyclic nature, enabling easier manipulation and simplification of complex expressions involving i.

exponent simplification

Exponent simplification is an important technique when working with powers of the imaginary unit i. To simplify the exponent of i, we utilize its periodicity. For instance, any exponent can be reduced by dividing it by 4 and using the remainder to determine the equivalent lower power of i. Consider the example \i^{-12}\ from the exercise: \[i^{-12} = (i^4)^{-3} = 1^{-3} = 1.\] Since \i^4 = 1\, any power that is a multiple of 4 is equivalent to 1. This significantly simplifies calculations. Therefore, simplifying \frac{1}{i^{-12}}\ becomes straightforward: \[ \frac{1}{i^{-12}} = \frac{1}{1} = 1.\] By mastering the cyclic pattern and simplifying exponents, handling complex numbers involving i becomes far less intimidating and more manageable.