Cho f(x) = sinx và \(\mathop {\lim }\limits_{x \to...

C

- Hướng dẫn giải

\(\mathop {\lim }\limits_{x \to {\rm{\pi }}} \frac{{\sin \;x}}{{x - {\rm{\pi }}}} =  - 1 \Leftrightarrow \mathop {\lim }\limits_{x \to \pi } \frac{{f\left( x \right) - f\left( \pi  \right)}}{{x - \pi }} =  - 1 \Rightarrow f'\left( \pi  \right) =  - 1\)