Imaginary numbers are divided into pure imaginary numbers and impure imaginary numbers. The square of pure imaginary number ai = the negative of the square of a, where a is a real number and not equal to 0. Impure imaginary number a+bi, a and b are real numbers, which are not equal to 0.
The term number was founded by Descartes, a famous mathematician in the17th century, because the concept at that time thought it was a nonexistent real number. Later, it was found that the real part A of the imaginary number a+b*i can correspond to the horizontal axis and the imaginary part B can correspond to the vertical axis on the plane, so that the imaginary number a+b*i can correspond to the points (a, b) on the plane.
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In the book Geometry (French: La Géométrie) written by Descartes, a famous mathematician in the17th century, it was named nombre imaginaire, which became the origin of the word imaginary number.
Later, through the study of Euler and Gauss, it was found that the imaginary number can correspond to the vertical axis on the plane, which is as real as the horizontal axis on the real number. The plane formed by the imaginary axis and the real axis is called the complex plane, and each point on the complex plane corresponds to a complex number.
In geometry, the longitudinal axis of the complex plane represents imaginary numbers, and they are perpendicular to the horizontal axis representing real numbers. One way to look at imaginary numbers is to consider the standard number line: it increases positively to the right and decreases negatively to the left. At 0 o'clock on the X axis, you can draw the "positive" imaginary number of the Y axis upwards, and then increase it upwards; The "negative" imaginary number increases downward.
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