Derivative of inverse trig functions.

[jrjack]

Homework Statement

Find the derivative:
y=sec^-1(1/2t³)

Homework Equations

\frac{\frac{du}{dx}}{|u|\sqrt{u^2-1}}

The Attempt at a Solution

I have an example to follow, but I don't know how step 1. became step 2.?...or more exactly the last part under the radical? (1-4t^6) instead of just -1 ?

1.y'=\frac{\frac{-3}{2t^4}}{|\frac{1}{2t^3}|\sqrt{(\frac{1}{2t^3})^2-1}}

2.y'=\frac{-3}{(t)\sqrt{\frac{1}{4t^6}(1-4t^6)}}

 

[jrjack]

Nevermind... I see it now.