f is a real valued function and not identically zero satisfying f(x+y)+f(x-y) = 2f(x)f(y) for all x,y belonging to R then it is what type of function even or odd ? How?
f is a real valued function and not identically zero satisfying f(x+y)+f(x-y) = 2f(x)f(y) for all x,y belonging to R then it is what type of function even or odd ? How?