Let f be a real-valued function defined on the inte-
rval [−1, 1]. If the area of the equilateral triangle with
(0, 0) and (x, f(x)) as two vertices is (√3)/4, then f(x)
is equal to
(A) (√(1−x^2 )) (B) (√(1+x^2 ))
(C) −(√(1−x^2 )) (D) −(√(1+x^2 ))
If f:R→R is a function such that f(0)=1 and f(x+f(y))=
f(x)+y for all x, y∈R, then
(A) 1 is a period of f
(B) f(n)=1 for all integers n
(C) f(n)=n for all integers n
(D) f(−1)=0