Is i^2 = -1?


Is {eq}i^2 = -1 {/eq}?

Complex Numbers

When working in mathematics, we often work only with real numbers. However, this is only a small set of all of the possible numbers that we can work with. Complex numbers are numbers of the form {eq}a + bi {/eq}, where {eq}i = \sqrt{-1} {/eq}. If {eq}b = 0 {/eq}, this is a real number, so all real numbers are also complex numbers.

Answer and Explanation:


Recall that the imaginary unit is defined as {eq}i = \sqrt{-1} {/eq}. What would happen if we squared both sides of this expression?

{eq}i = \sqrt{-1}\\ i^2 = \sqrt{-1}^2\\ i^2 = \sqrt{-1}\cdot \sqrt{-1} = -1 {/eq}

Therefore, this statement is true.

Learn more about this topic:

What is an Imaginary Number?

from Math 101: College Algebra

Chapter 5 / Lesson 1

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