Phương trình \[\cos 11x\cos 3x = \cos 17x\cos 9x\] có nghiệm là:

A.m = −3

B.m = −2      

C.m = 0

D.m = 3

A.\[x = \frac{\pi }{8} + k\pi \left( {k \in Z} \right)\]

B. \[x = \frac{\pi }{8} + \frac{{k\pi }}{5}\left( {k \in Z} \right)\]

C. \[x = \frac{\pi }{8} + \frac{{k\pi }}{4}\left( {k \in Z} \right)\]

D. \[x = \frac{\pi }{8} + \frac{{k\pi }}{2}\left( {k \in Z} \right)\]

A.\[x = \frac{{k\pi }}{2}\,\,\left( {k \in Z} \right)\]

B. \[x = k\pi \,\,\left( {k \in Z} \right)\]

C. \[x = k2\pi \,\,\left( {k \in Z} \right)\]

D. Kết quả khác

A.\[x = \frac{\pi }{2}\]

B. \[x = \pi \]

C. \[x = 0\]

D. \[x = - \frac{\pi }{2}\]

A.980

B.51

C.981

D.1000

A.\[k2\pi \left( {k \in Z} \right)\]

B. \[k\pi \left( {k \in Z} \right)\]

C. \[\pi + k2\pi \left( {k \in Z} \right)\]

D. Cả 3 đáp án đúng

A.\[\left[ {\begin{array}{*{20}{c}}{x = \alpha + k\pi }\\{x = \pi - \alpha + k\pi }\end{array}} \right.(k \in Z)\]

B. \[\left[ {\begin{array}{*{20}{c}}{x = \alpha + k2\pi }\\{x = \pi - \alpha + k2\pi }\end{array}} \right.(k \in Z)\]

C. \[\left[ {\begin{array}{*{20}{c}}{x = \alpha + k2\pi }\\{x = - \alpha + k2\pi }\end{array}} \right.(k \in Z)\]

D. \[\left[ {\begin{array}{*{20}{c}}{x = \alpha + k\pi }\\{x = - \alpha + k\pi }\end{array}} \right.(k \in Z)\]