[Differential Calculus]Trigonometric Limits (special case)

The problem is: lim (theta) -> 0 [(cos^(2)(theta) - 1)/(theta)]

I know the answer is zero, and that I'm supposed to morph it into the special case of [(cos(x)-1)/(x)] = 0, but I cannot even come up with the first step...any tips would be appreciated.

My first thought was to use the pythagreon identity -sin^(2)(u) = cos^(2)(u)-1...but I can't seem to get anywhere with -sin^(2)(u).

Thanks.