i thought it was 25*sec^2(5x)*tan^2(5x) but it wrong.
could i get some help with the second derivative please =)
thank you
chad
I don't see a factor of "2" in your coefficient. Of course, the derivative of [tex]x^2[tex] is 2x so the derivative of is 5(2 sec(5x)) times the derivative of sec(5x).