I have to find the first derivative of y= ln((1-cos(x))/(1+cos(x)))

the derivative of the ln is 1+cos(x)/1-cos(x)

and the derivative of the inner function is:

((1+cosx) (sinx) - (1-cos(x) (-sinx)

-----------------------------------

(1+cos(x))^2

i then multiplied and got

(1+cos(x))(sinx + sinxcosx+sinx-sinxcosx)

----------------------------

(1+cos(x))^2 * 1-cos(x)

to clean this up:

2sinx * (1+cos(x))

---------------------------- = y'

(1+cos(x))^2 * 1-cos(x)

After canceling out stuff:

2sinx

------------------- = y'

1-cosx^2

but the answer says:

- 2sinx

------------------- = y'

cosx^2-1

Is this merely a matter of just multiplying both of these by -1??