In mathematics, a number with a negative square is defined as a pure imaginary number. All imaginary numbers are complex numbers. Defined as I 2 =-1. But the imaginary number has no arithmetic root, so √ (-1) = i. For z=a+bi, it can also be expressed in the form of iA power of e, where e is constant, I is imaginary unit, and A is imaginary amplitude, which can be expressed as z=cosA+isinA. A pair of numbers consisting of real numbers and imaginary numbers is regarded as a number within the range of complex numbers, so it is called a complex number. Imaginary number is neither positive nor negative. Complex numbers that are not real numbers, even pure imaginary numbers, cannot compare sizes. This number has a special symbol "I" (imaginary number), which is called imaginary unit. But in electronics and other industries, because I is usually used to represent current, the imaginary unit is represented by J.

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