Alphabeta Math

The Complex Exponential and Euler's Formula

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✓ 19 results · all verified · 0 also independently AI-judged
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1 · Prerequisites
Abstract Algebra
Combinatorics
Linear Algebra
Real Analysis
Set Theory
Topology
2 · Logical flowchart

3 · Items

Definition

Integer powers in the complex field

Lemma

The binomial theorem over the complex field

Definition

The Euclidean metric, convergence, Cauchy sequences, and continuity on the complex plane

Theorem

The complex plane is complete, and convergence is equivalent to convergence of real and imaginary parts

Definition

Complex series, absolute convergence, complex power series, and radius of convergence

Theorem

Every absolutely convergent complex series converges, and rearrangements preserve its sum

Theorem

Cauchy-Hadamard for complex power series, including zero and infinite radius

Lemma

The Cauchy product of two absolutely convergent complex series converges absolutely to the product of their sums

Lemma

The complex exponential series converges absolutely for every complex argument

Definition

The complex exponential by its power series

Theorem

exp(z+w)=exp z exp w, and the complex exponential extends the real exponential

Theorem

Euler's formula: exp(iθ)=cosθ+i sinθ for every real θ

Corollary

exp(x+iy)=eˣ(cos y+i sin y), |exp(x+iy)|=eˣ, and e^iπ+1=0

Theorem

ker(exp)=2π iℤ, and exp z=exp w exactly when z-w∈2π iℤ

Theorem

Every nonzero complex number has a unique polar form r(cosθ+i sinθ) with r>0 and -π<θ≤π

Theorem

The complex exponential maps ℂ onto ℂ∖{0}

Corollary

Complex de Moivre formula for every integer exponent

Theorem

The n-th roots of a complex number and the n distinct roots of unity for every n≥1

Corollary

For n≥2, the sum of all n-th roots of unity is zero

Definition

Complex logarithms, the principal logarithm, and principal and multivalued complex powers

Theorem

All logarithms of z≠0 are Logz+2π i k, k∈ℤ

Theorem

There is no continuous logarithm on all of ℂ∖{0}

Definition

Complex sine, cosine, hyperbolic sine, and hyperbolic cosine from the complex exponential

Theorem

The exponential formulas, real restrictions, and trigonometric-hyperbolic dictionary over ℂ

Definition

Formal complex polynomials, evaluation, degree, leading coefficient, and monic polynomials

Lemma

A nonconstant complex polynomial tends to infinite modulus and attains a global minimum modulus

Lemma

A nonzero value of a nonconstant complex polynomial cannot be a local minimum of its modulus

Theorem

Fundamental theorem of algebra: every nonconstant complex polynomial has a complex root

Sources