Phương trình \(\cos \left( {x + \pi } \right) = 1...

Câu hỏi: Phương trình \(\cos \left( {x + \pi } \right) = 1 + \sin \left( {{x \over 2} + {\pi  \over 2}} \right)\) có nghiệm là:

A \(\left[ \matrix{x = \pi + k2\pi \hfill \cr x = \pm {{4\pi } \over 3} + k4\pi \hfill \cr} \right.\,\,\left( {k \in Z} \right)\)

B \(\left[ \matrix{x = \pi + k2\pi \hfill \cr x = \pm {{4\pi } \over 3} + k2\pi \hfill \cr} \right.\,\,\left( {k \in Z} \right)\)

C \(\left[ \matrix{x = {\pi \over 4} + k\pi \hfill \cr x = \pm {\pi \over 3} + k\pi \hfill \cr} \right.\,\,\left( {k \in Z} \right)\)

D \(\left[ \matrix{x = - {\pi \over 4} + k\pi \hfill \cr x = \pm {\pi \over 6} + k\pi \hfill \cr} \right.\,\,\left( {k \in Z} \right)\)