6. Find the derivative of y = arccos 4x with respect to x. 4 a. b 1-4x2 VI-4x2 - 4 -4 C. d. (4x)2 -1 VI -(4x)2 21. Evaluate - dx x2 + 2.x +5 a. arctan (x+1) +c b. YAarctan (+1) +c c. V2arctan (*+ 1/+c d. arctan (x+1)/+c 24. Evaluate sin 2xsin 4xdx - sin ' 2.x + C b. - sin 3 2x + C 1- WI . - cos' 2x + C . - cos 2x + C 2