Mathematics ACT Aspire Test 2025 – 400 Free Practice Questions to Pass the Exam

In the context of complex numbers, the variable "i" specifically represents the square root of -1. This concept is fundamental in mathematics, particularly in the field of complex numbers, where "i" is used to extend the real number system to include the solutions to equations that do not have real solutions, such as x² + 1 = 0.

When we say that "i" equals the square root of -1, we are essentially saying that when you square "i", you get -1. This introduces the notion of imaginary numbers, which, when combined with real numbers, forms complex numbers of the form a + bi, where a is the real part and b is the imaginary part. This understanding of "i" is crucial for solving certain equations in advanced mathematics and for applications in engineering, physics, and other fields.

The other options do not accurately represent the definition of "i" in this context, as they pertain to different values in mathematics.