posted by Sasha .
If f(x) = sec x, find f''(π/4).
f'(x) = secxtanx then use the product rule and figure out the derivative of that:
f''(x) = tanxsecxtanx + secx sec^2x and then it becomes tan^2x + sec^3x.
then you plug in pi/4 which is 45 degrees.
it is (1)(1.41) + 2.83 and the answer is 4.24