A Cosine in Disguise

★ 6/10functions Recursion Functional Equations

Problem

A function $f$ on $\mathbb{R}$ satisfies $f(1) = \dfrac14$ and

4f(x)f(y) = f(x+y) + f(x-y).

Find $f(2016)$ .

Answer

Solution

Difficulty	6/10
Topics	functions, Recursion, Functional Equations

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