Phương trình \(\cos \left( {2x + {\pi  \over 4}} \...

Câu hỏi: Phương trình \(\cos \left( {2x + {\pi  \over 4}} \right) + \cos \left( {2x - {\pi  \over 4}} \right) + 4\sin x = 2 + \sqrt 2 \left( {1 - \sin x} \right)\) có nghiệm là:

A \(\left[ \matrix{x = {\pi \over {12}} + k2\pi \hfill \cr x = {{11\pi } \over {12}} + k2\pi \hfill \cr} \right.\,\,\,\,\left( {k \in Z} \right)\)

B \(\left[ \matrix{x = {\pi \over 6} + k2\pi \hfill \cr x = {{5\pi } \over 6} + k2\pi \hfill \cr} \right.\,\,\,\,\left( {k \in Z} \right)\)

C \(\left[ \matrix{x = {\pi \over 3} + k2\pi \hfill \cr x = {{2\pi } \over 3} + k2\pi \hfill \cr} \right.\,\,\,\,\left( {k \in Z} \right)\)

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