The value of k (k < 0) for which the function f defined as f(x) = \(\left\{ {\begin{array}{*{20}{c}} {\frac{{1 - \cos kx}}{{x\sin x}}}&{,x \ne 0}\\ {\frac{1}{2}}&{,x = 0} \end{array}} \right.\) is continuous at x = 0 is :
1
± 1
2
-1
3
± \(\frac{1}{2}\)
4
\(\frac{1}{2}\)