Finding Points of Inflection In Exercises 15 36 find the points of inflection and discuss the concavity of the graph of the function 15 f x x 9x 24x18 16 f x x 6x 5 17 f x 2 7 x 18 f x 4x 3x 19 f x x x 4 20 f x x 2 x 1 21 f x x x 3 22 f x x 9 x 6 x 23 x 25 f x sin 0 47 2 24 f x 33 y x ln x 35 f x arcsin 4 5 27 f x sec x 0 47 28 f x sin x cos x 0 2 29 f x 2 sin x sin 2x 0 27 30 f x x 2 cos x 0 2n 31 y e 3 x x 3 x 26 f x 2 csc 3x 21 32 y e ex 34 y In x 9 36 f x arctan x2 0 2