Mathematically, real numbers are defined as the number of corresponding points on the number axis. Real numbers can be intuitively regarded as one-to-one correspondence between finite decimals and infinite decimals, and between real numbers and points on the number axis. But the whole of real numbers can't be described only by enumeration. Real and imaginary numbers * * * make up a complex number.
Real numbers can be used to measure continuous quantities. Theoretically, any real number can be expressed as an infinite decimal, and to the right of the decimal point is an infinite series. In fact, real numbers are usually approximated to finite decimals. In the computer field, because computers can only store a limited number of decimal places, real numbers are often represented by floating-point numbers.
nature
(1) closed: the real number set is closed for the four operations of addition, subtraction, multiplication and division (divisor is not zero), that is, the sum, difference, product and quotient of any two real numbers (divisor is not zero) are still real numbers.
(2) Orderliness: the set of real numbers is ordered, that is, any two real numbers must satisfy and only satisfy one of the following three relationships ab.
(3) transitivity: the real number size is transitive, that is, if a >；; D and b>c, there is a> C.