iff ( x ) = x + cos(x), what isf"(x)? of" (x) =2 - cos(x) of"(x) = -2+ sin(x) of"(x) = -2+ cos(x) of"(x) = 2+ cos(x) Which statement is true? O If f(x) is increasing, and f "(x) is positive, then f '(x) is positive and f is concave up. O If f(x) is increasing, and f "(x) is positive, then f '(x) is negative and f is concave up. O If f(x) is increasing, and f "(x) is positive, then f '(x) is positive and f is concave down. O If f(x) is increasing, and f "(x) is positive, then f '(x) is positive and f is concave down. If(x) = [sin(x)]", what isf (x)? Enter the answer in the box. f' ( x ) =