MathDB
Very beautiful functional equation involving trigonometry

Source: Moldova TST for IMO 2020

March 7, 2020
algebrafunctional equationfunctiontrigonometry

Problem Statement

Find all functions f:[1,1]R,f:[-1,1] \rightarrow \mathbb{R}, which satisfy f(sinx)+f(cosx)=2020f(\sin{x})+f(\cos{x})=2020 for any real number x.x.