\(\mathop {\lim }\limits_{x \to \frac{\pi }{4}} \f...

Câu hỏi: \(\mathop {\lim }\limits_{x \to \frac{\pi }{4}} \frac{{{\mathop{\rm s}\nolimits} {\rm{inx}} - c{\rm{osx}}}}{{\tan \left( {\frac{\pi }{4} - x} \right)}}\) bằng

A. 0

B. \( + \infty \)

C. \( - \sqrt 2 \)

D. \(\frac{1}{2}\)