Exponential on Complex Plane is Group Homomorphism
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Theorem
Let $\struct {\C, +}$ be the additive group of complex numbers.
Let $\struct {\C_{\ne 0}, \times}$ be the multiplicative group of complex numbers.
Let $\exp: \struct {\C, +} \to \struct {\C_{\ne 0}, \times}$ be the mapping:
- $x \mapsto \map \exp x$
where $\exp$ is the complex exponential function.
Then $\exp$ is a group homomorphism.
Proof
If $z \in \C$, then by the definition of the complex exponential function, $\exp$ is a mapping $\C \to \C_{\ne 0}$.
Let $z_1, z_2 \in \C$.
- $\map \exp {z_1 + z_2} = \map \exp {z_1} \, \map \exp {z_2}$
Therefore $\exp: \struct {\C, +} \to \struct {\C_{\ne 0}, \times}$ is a group homomorphism.
$\blacksquare$
Sources
- 1978: Thomas A. Whitelaw: An Introduction to Abstract Algebra ... (previous) ... (next): $\S 47$. Homomorphisms and their elementary properties: Illustration