Help me with my Derivative!?

Question

y = 4(sec((x/2)-1)
need to find 1st and 2nd derivative
PLEASE HELP!!

Answer 1

Not to worry, the secant is 1/cos, so this can be written as 4 [ 1/cos(x/2) -1 ]. Cos-1(u) is treated as any function (ie" f'(cos-1(u) = -(du/dx) (sinu)/(cos^2(u). Note that sin(u)/cos^2(u) = tan(u)sec(u), you may see the answer to the 1st derivitive in that form.