| Version 3 |
Version 2 |
| A functional equation is an equation whose unknowns are functions. |
A functional equation is an equation whose unknowns are functions. |
| $f(x+y) = f(x) + f(y),\quad f(x\cdot y) = f(x) \cdot f(y)$ are examples of such |
$f(x+y) = f(x) + f(y),\quad f(x\cdot y) = f(x) \cdot f(y)$ are examples of such |
| equations. The systematic study of these didn't begin before the 1960's, |
equations. The systematic study of these didn't begin before the 1960's, |
| although various mathematicians have been studying them before, including |
although various mathematicians have been studying them before, including |
| Euler and Cauchy just to mention a few. |
Euler and Cauchy just to mention a few. |
| Functional equations appear many places, for example |
Functional equations appear many places, for example |
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the gamma function and Riemann's zeta function both satisfy functional equations.
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the gamma function and Riemann's zeta function both satisfies functional equations.
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