Help me do my homework.

Can someone who's better at math than me help me out here?

How do I calculate the derivative of v with respect to t in the formula:

v=sqr(c² – t₀²c²/t²)

And once I get that, I'll need the second derivative as well. Calculus was a very long time ago and I'm afraid I'm rather rusty...

( Why do I want to know this? )