#### legacyofpiracy

##### Junior Member

- Joined
- Oct 20, 2005

- Messages
- 82

Using the formula of the derivative of an arctan : (1/(1+u)^2)*(du/dx)

I tried to find the derivative of this equation:

f(x)=2arctan(8x^7)

i ended up getting this

2*(1/(1+(8x^7))^2)*(56x^6)*(7x+7)

also for the equation f(x)=tan^-1(cos(8x))

i ended up getting

(1/1+(cos(8x))^2)*(-sin(8x))+8

there really wasnt any work to show..i simply followed the formula of the arctan and took the derivative of the u. Still..any guesses where I might have gone wrong?