TheoremBase

The Earlier and the New Versions of the Definitions of the Natural Numbers, the Complex Numbers, the Conjugate and the Modulus Agree, and the Two Versions of Real Correspond

The earlier and the new versions of the definitions of the natural numbers, the complex numbers, the complex conjugate and the modulus define the same objects, and the two versions of Real correspond element by element, preserving the operations and the order.

Statement

In the setting of The Complex Numbers, with the Real Numbers Identified with a Subset of the Complex Numbers.

Natural numbers. The set N\mathbb{N} of natural numbers and the number 11 of The Set of Natural Numbers and the Number One (ii) are the set N\mathbb{N} of natural numbers and the number 11 of The Set of Natural Numbers and the Number One (ii).

Complex numbers. The set C\mathbb{C} of complex numbers of the earlier version, its sum and product and its imaginary unit ii are the set of complex numbers of the new version, its sum and product and its imaginary unit.

Complex conjugate. For every complex number zz, the complex conjugate z‾\overline{z} of zz in the earlier version is the complex conjugate of zz in the new version.

Modulus. For every complex number zz, the modulus ∣z∣|z| of zz in the earlier version and the modulus of zz in the new version are the same real number.

The two versions of Real. For an element xx of Real\mathrm{Real} in the sense of The Real Numbers as a Type (i), let x^\hat{x} be the element of Real\mathrm{Real} in the sense of The Real Numbers as a Type (i) with the same set. Then x↦x^x\mapsto\hat{x} is a one-to-one correspondence between the two, and, with 00, 11, ++, ⋅\cdot, −-, ≤\le and << on each side as in The Real Numbers as a Type (ii) and The Real Numbers as a Type (ii), for all xx and yy

0^=0,1^=1,x+y^=x^+y^,x⋅y^=x^⋅y^,−x^=−x^,x−y^=x^−y^,x≤y  ⟺  x^≤y^,x<y  ⟺  x^<y^;\hat{0}=0,\quad \hat{1}=1,\quad \widehat{x+y}=\hat{x}+\hat{y},\quad \widehat{x\cdot y}=\hat{x}\cdot\hat{y},\quad \widehat{-x}=-\hat{x},\quad \widehat{x-y}=\hat{x}-\hat{y},\quad x\le y\iff\hat{x}\le\hat{y},\quad x<y\iff\hat{x}<\hat{y};

hence the correspondence also preserves numerals and powers, read as in The Real Numbers as a Type (iii) and The Real Numbers as a Type (iii): for every natural number nn, every integer ii and every xx, it maps nn to nn, ii to ii, xnx^{n} to x^n\hat{x}^{n}, n⋅xn\cdot x to n⋅x^n\cdot\hat{x} and i⋅xi\cdot x to i⋅x^i\cdot\hat{x}. For x≠0x\ne0, the reciprocal of xx is mapped to the reciprocal of x^\hat{x}.

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