Evaluating a Second Derivative In Exercises 89–92, evaluate the second derivative of the function at the given point. Use a computer algebra system to verify your result. 89. h(x) = 1 9 (3x + 1)3 , (1, 64 9 ) 90. f(x) = 1 √x + 4 , (0, 1 2) 91. f(x) = cos x2 , (0, 1) 92. g(t) = tan 2t, ( π 6 , √3)