Phương trình lượng giác thường gặp !!

A.\(\left[ {\begin{array}{*{20}{c}}{x = \frac{{k\pi }}{2}}\\{x = \pm \frac{1}{2}arccos( - \frac{1}{6}) + k\pi }\end{array}} \right.(k \in Z)\)

B. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{{k\pi }}{2}}\\{x = \pm \frac{5}{2}arccos( - \frac{1}{6}) + k\pi }\end{array}} \right.(k \in Z)\)

C. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{{k\pi }}{2}}\\{x = \pm \frac{1}{2}arccos( - \frac{1}{3}) + k\pi }\end{array}} \right.(k \in Z)\)

D. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{{k\pi }}{2}}\\{x = \pm \frac{1}{3}arccos( - \frac{1}{6}) + k\pi }\end{array}} \right.(k \in Z)\)

A.\(\left\{ {\begin{array}{*{20}{c}}{x = \frac{\pi }{6} + k2\pi }\\{y = - \frac{\pi }{6} + k2\pi }\end{array}} \right.(k \in Z)\)

B. \(\left\{ {\begin{array}{*{20}{c}}{x = \frac{{2\pi }}{3} + k2\pi }\\{y = \frac{\pi }{3} - k2\pi }\end{array}} \right.(k \in Z)\)

C. \(\left\{ {\begin{array}{*{20}{c}}{x = \frac{{2\pi }}{3} + k2\pi }\\{y = \frac{\pi }{3} + k2\pi }\end{array}} \right.(k \in Z)\)

D. \(\left\{ {\begin{array}{*{20}{c}}{x = \frac{\pi }{6} + k2\pi }\\{y = \frac{\pi }{6} + k2\pi }\end{array}} \right.(k \in Z)\)

A.\(\left[ {\begin{array}{*{20}{c}}{x = \frac{\pi }{3} + k\pi }\\{x = \frac{\pi }{6} + k\pi }\end{array}} \right.(k \in Z)\)

B. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{\pi }{3} + k2\pi }\\{x = \frac{\pi }{6} + k2\pi }\end{array}} \right.(k \in Z)\)

C. \(\left[ {\begin{array}{*{20}{c}}{x = - \frac{\pi }{3} + k\pi }\\{x = - \frac{\pi }{6} + k\pi }\end{array}} \right.(k \in Z)\)

D. \(\left[ {\begin{array}{*{20}{c}}{x = - \frac{\pi }{3} + k2\pi }\\{x = \frac{\pi }{6} + k\pi }\end{array}} \right.(k \in Z)\)

A.\[x = \pm \frac{\pi }{6} + k\pi \,\,\left( {k \in Z} \right)\]

B. \[x = \pm \frac{\pi }{6} + k2\pi \,\,\left( {k \in Z} \right)\]

C. \[x = \pm \frac{\pi }{3} + k\pi \,\,\left( {k \in Z} \right)\]

D. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{\pi }{6} + k\pi \,\,\left( {k \in Z} \right)}\\{x = \frac{\pi }{3} + k\pi \,\,\left( {k \in Z} \right)}\end{array}} \right.\)

A.\[x = - \frac{\pi }{6} + k2\pi \,\,\,\left( {k \in Z} \right)\]

B. \[x = \frac{\pi }{6} + \frac{{k2\pi }}{3}\,\,\,\left( {k \in Z} \right)\]

C. \[x = - \frac{\pi }{6} + \frac{{k2\pi }}{3}\,\,\,\left( {k \in Z} \right)\]

D. \[x = \pm \frac{\pi }{6} + \frac{{k2\pi }}{3}\,\,\,\left( {k \in Z} \right)\]

A.0     

B.1     

C.2      

D.4

A.\(\left[ {\begin{array}{*{20}{c}}{x = k\pi }\\{x = \frac{\pi }{3} + k\pi }\end{array}} \right.(k \in \mathbb{Z})\)

B. \(\left[ {\begin{array}{*{20}{c}}{x = k\pi }\\{x = \frac{{2\pi }}{3} + k2\pi }\end{array}} \right.(k \in \mathbb{Z})\)

C. \(\left[ {\begin{array}{*{20}{c}}{x = k2\pi }\\{x = \frac{{2\pi }}{3} + k2\pi }\end{array}} \right.(k \in \mathbb{Z})\)

D. \(\left[ {\begin{array}{*{20}{c}}{x = k\pi }\\{x = \frac{{2\pi }}{3} + k\pi }\end{array}} \right.(k \in \mathbb{Z})\)

A.m=1

B.Không có m

C.m=0

D.Với mọi m

A.Có 1 họ nghiệm

B.Có 2 họ nghiệm

C.Vô nghiệm     

D.Có 1 nghiệm duy nhất

A.0     

B.1

C.2

D.3

A.\[ - \frac{{5{\pi ^2}}}{{12}}\]

B. \[ - \frac{{5{\pi ^2}}}{{144}}\]

C. \[\frac{{5{\pi ^2}}}{{144}}\]

D. \[\frac{{{\pi ^2}}}{{12}}\]

A.\[\frac{{3\pi }}{5}\]

B. \[\frac{{29\pi }}{{30}}\]

C. \[\frac{{5\pi }}{6}\]

D. \[\frac{{23\pi }}{{30}}\]

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

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

C. \[x = \frac{\pi }{6} + k2\pi \,\,\left( {k \in \mathbb{Z}} \right)\]

D. Tất cả đều đúng.

A.\(\left[ {\begin{array}{*{20}{c}}{x = \frac{\pi }{2} + k\pi }\\{x = \frac{\pi }{6} + k\pi }\end{array}} \right.(k \in Z)\)

B. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{\pi }{4} + k\pi }\\{x = \frac{\pi }{3} + k\pi }\end{array}} \right.(k \in Z)\)

C. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{\pi }{8} + k2\pi }\\{x = \frac{\pi }{{12}} + k2\pi }\end{array}} \right.(k \in Z)\)

D. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{\pi }{8} + k\pi }\\{x = \frac{\pi }{{12}} + k\pi }\end{array}} \right.(k \in Z)\)

A.Ba nghiệm      

B.Một nghiệm     

C.Hai nghiệm

D.Bốn nghiệm

A.0

B.1     

C.2

D.3

A.9

B.3

C.6

D.7

A.\[m \ne \frac{1}{2}\]

B. \[m = \frac{1}{2}\]

C. \(\left\{ {\begin{array}{*{20}{c}}{\frac{1}{3} < m < 1}\\{m \ne \frac{1}{2}}\end{array}} \right.\)

</>

D. \[\frac{1}{3} < m < 1\]

</>

A.\[x = \frac{\pi }{9} + \frac{{k2\pi }}{3};\left( {k \in \mathbb{Z}} \right)\]

B. \[x = \frac{\pi }{{18}} + \frac{{k\pi }}{6};\left( {k \in \mathbb{Z}} \right)\]

C. \[x = \pm \frac{\pi }{6} + \frac{{k\pi }}{2}\,\,\left( {k \in \mathbb{Z}} \right)\]

D. \[x = \frac{\pi }{{18}} + \frac{{k\pi }}{3};\,\,x = - \frac{\pi }{6} + \frac{{k\pi }}{2}\,\,\left( {k \in \mathbb{Z}} \right)\]

A.\[x = - \frac{\pi }{4} + k\pi ;\,\,x = \frac{\pi }{6} + k2\pi ;x = \frac{{5\pi }}{6} + k2\pi ;\,\,x = - \frac{\pi }{2} + k2\pi \left( {k \in \mathbb{Z}} \right)\]

B. \[x = \frac{\pi }{4} + k2\pi ;\,\,x = - \frac{\pi }{6} + k2\pi ;x = \frac{{5\pi }}{6} + k\pi ;\,\,x = - \frac{\pi }{2} + k\pi \left( {k \in \mathbb{Z}} \right)\]

C. \[x = \pm \frac{\pi }{6} + k2\pi ;x = \frac{{5\pi }}{6} + k2\pi ;\,\,x = - \frac{\pi }{2} + k2\pi \left( {k \in \mathbb{Z}} \right)\]

D. \[x = - \frac{\pi }{8} + k\pi ;\,\,x = \frac{\pi }{6} + k\pi ;x = - \frac{{5\pi }}{6} + \frac{{k\pi }}{6};\,\,x = - \frac{\pi }{2} + \frac{{k\pi }}{6}\left( {k \in \mathbb{Z}} \right)\]

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

B. \[x = \frac{{2\pi }}{3} + 2k\pi \,\,\left( {k \in \mathbb{Z}} \right)\]

C. \[x = \frac{\pi }{3} + 2k\pi \,\,\left( {k \in \mathbb{Z}} \right)\]

D. \[x = \frac{{k\pi }}{3}\,\,\left( {k \in \mathbb{Z}} \right)\]

A. Vô nghiệm 

B. $x=\frac{\pi }{6}+\frac{k2\pi }{3}\left(k\in \mathbb{Z}\right)$ hoặc $x=\frac{k2\pi }{3}\left(k\in \mathbb{Z}\right)$

C. $x=\frac{\pi }{6}+k2\pi \left(k\in \mathbb{Z}\right)$

D. $x=\frac{\pi }{6}+\frac{k\pi }{3}\left(k\in \mathbb{Z}\right)$

A.\[x = \frac{{n\pi }}{2};\,\,x = \frac{\pi }{{20}} + \frac{{k\pi }}{{13}}\,\,\left( {k,\,\,n \in \mathbb{Z}} \right)\]

B. \[x = n\pi ;\,\,x = \frac{\pi }{{20}} + \frac{{k\pi }}{{10}}\,\,\left( {k,\,\,n \in \mathbb{Z}} \right)\]

C. \[x = n\pi ;\,\,x = \frac{{3\pi }}{5} + \frac{{2k\pi }}{7}\,\,\left( {k,\,\,n \in \mathbb{Z}} \right)\]

D. \[x = n\pi ;\,\,x = \frac{{3\pi }}{5} + \frac{{7k\pi }}{{13}}\,\,\left( {k,\,\,n \in \mathbb{Z}} \right)\]

C. \[x = \pm \frac{\pi }{6} + k\pi ;\,\,x = - \frac{\pi }{{12}} + \frac{{k\pi }}{2}\,\,\left( {k \in \mathbb{Z}} \right)\]

A.\[x = \pm \frac{\pi }{3} + k2\pi ;\,\,x = \frac{{2\pi }}{3} + k2\pi \,\,\left( {k \in \mathbb{Z}} \right)\]

B. \[x = \frac{\pi }{4} + k\pi ;\,\,x = \frac{\pi }{6} + k\pi \,\,\left( {k \in \mathbb{Z}} \right)\]

C. \[x = k\pi ;\,\,x = \frac{\pi }{3} + k2\pi ;\,\,x = \frac{{2\pi }}{3} + k2\pi \,\,\left( {k \in \mathbb{Z}} \right)\]

D. \[x = \frac{\pi }{2} + k\pi ;\,\,x = \frac{\pi }{6} + \frac{{k\pi }}{3}\,\,\left( {k \in \mathbb{Z}} \right)\]

A.\[x = \frac{{k\pi }}{{18}};\,\,x = \frac{{k\pi }}{{22}}\,\,\left( {k \in \mathbb{Z}} \right)\]

B. \[x = \frac{{k\pi }}{9};\,\,x = \frac{\pi }{{44}} + \frac{{k\pi }}{{22}}\,\,\left( {k \in \mathbb{Z}} \right)\]

C. \[x = \frac{\pi }{3} + \frac{{k\pi }}{{18}};\,\,x = \frac{\pi }{{22}} + \frac{{k\pi }}{{22}}\,\,\left( {k \in \mathbb{Z}} \right)\]

D. \[x = \frac{{k\pi }}{3};\,\,x = \frac{\pi }{{44}} + \frac{{k\pi }}{{44}}\,\,\left( {k \in \mathbb{Z}} \right)\]

A.\[x = k\pi ,x = \frac{\pi }{6} + \frac{{k\pi }}{3},x = \frac{\pi }{{12}} + k\pi ,x = \frac{{5\pi }}{7} + k\pi \]

B. \[x = k2\pi ,x = \frac{{7\pi }}{6} + k2\pi ,x = - \frac{\pi }{6} + k2\pi ,x = \frac{{7\pi }}{6} + k2\pi \]

C. \[x = k\pi ,x = \frac{\pi }{3} + \frac{{k2\pi }}{3},x = \frac{\pi }{{12}} + k\pi ,x = \frac{{5\pi }}{{12}} + k\pi \]

D. \[x = k2\pi ,x = \frac{\pi }{6} + \frac{{k2\pi }}{3},x = \frac{\pi }{{12}} + k\pi ,x = \frac{{7\pi }}{{12}} + k\pi \]

A.\[x = \frac{\pi }{2} + k\pi ,x = \pm \frac{1}{5}\arccos \frac{{1 + \sqrt {17} }}{8} + k\pi ,x = \pm \frac{1}{5}\arccos \frac{{1 - \sqrt {17} }}{8} + k\pi \]

B. \[x = \pm \frac{\pi }{6} + k\pi \]

C. \[x = \pm \frac{1}{2}\arccos \frac{{1 + \sqrt {15} }}{7} + k\pi ,x = \pm \frac{1}{2}\arccos \frac{{1 - \sqrt {15} }}{7} + k\pi \]

D. \[x = \frac{\pi }{2} + k\pi ,x = \pm \frac{1}{2}\arccos \frac{{1 + \sqrt {17} }}{8} + k\pi ,x = \pm \frac{1}{2}\arccos \frac{{1 - \sqrt {17} }}{8} + k\pi \]

A. $\left[\begin{array}{c}x=\frac{k\pi }{2}\\ x=\pm \frac{1}{2}\arccos \left(-\frac{1}{6}\right)+k\pi \end{array}\right.\left(k\in Z\right)$

B. $\left[\begin{array}{c}x=\frac{k\pi }{2}\\ x=\pm \frac{5}{2}\arccos \left(-\frac{1}{6}\right)+k\pi \end{array}\right.\left(k\in Z\right)$

C. $\left[\begin{array}{c}x=\frac{k\pi }{2}\\ x=\pm \frac{1}{2}\arccos \left(-\frac{1}{3}\right)+k\pi \end{array}\right.\left(k\in Z\right)$

D. $\left[\begin{array}{c}x=\frac{k\pi }{2}\\ x=\pm \frac{1}{3}\arccos \left(-\frac{1}{6}\right)+k\pi \end{array}\right.\left(k\in Z\right)$

A. $x=\frac{\pi }{4}+k\pi \left(k\in Z\right)$

B. $x=\frac{\pi }{4}+\frac{k\pi }{2}\left(k\in Z\right)$

C. $x=\frac{3\pi }{4}+2k\pi \left(k\in Z\right)$

D. $x=\frac{3\pi }{4}+k\pi \left(k\in Z\right)$

A. $\left[\begin{array}{c}x=\frac{\pi }{3}+k\pi \\ x=\frac{\pi }{6}+k\pi \end{array}\right.\left(k\in Z\right)$

B. $\left[\begin{array}{c}x=\frac{\pi }{3}+k2\pi \\ x=\frac{\pi }{6}+k2\pi \end{array}\right.\left(k\in Z\right)$

C. $\left[\begin{array}{c}x=-\frac{\pi }{3}+k\pi \\ x=-\frac{\pi }{6}+k\pi \end{array}\right.\left(k\in Z\right)$

D. $\left[\begin{array}{c}x=-\frac{\pi }{3}+k2\pi \\ x=\frac{\pi }{6}+k\pi \end{array}\right.\left(k\in Z\right)$

A. $x=\pm \frac{\pi }{6}+k\pi \left(k\in Z\right)$

B. $x=\pm \frac{\pi }{6}+k2\pi \left(k\in Z\right)$

C. $x=\pm \frac{\pi }{3}+k\pi \left(k\in Z\right)$

D. $\left[\begin{array}{c}x=\frac{\pi }{6}+k\pi \left(k\in Z\right)\\ x=\frac{\pi }{3}+k\pi \left(k\in Z\right)\end{array}\right.$

C. 2      

A. $\left[\begin{array}{c}x=k\pi \\ x=\frac{\pi }{3}+k\pi \end{array}\right.\left(k\in Z\right)$

B. $\left[\begin{array}{c}x=k\pi \\ x=\frac{2\pi }{3}+k2\pi \end{array}\right.\left(k\in Z\right)$

C. $\left[\begin{array}{c}x=k2\pi \\ x=\frac{2\pi }{3}+k2\pi \end{array}\right.\left(k\in Z\right)$

D. $\left[\begin{array}{c}x=k\pi \\ x=\frac{2\pi }{3}+k\pi \end{array}\right.\left(k\in Z\right)$

A. $-\frac{5{\pi }^2}{12}$

B. $-\frac{5{\pi }^2}{144}$

C. $\frac{5{\pi }^2}{144}$

D. $\frac{{\pi }^2}{12}$

A. $x=\frac{k\pi }{18};x=\frac{k\pi }{22}\left(k\in Z\right)$

B. $x=\frac{k\pi }{9};x=\frac{\pi }{44}+\frac{k\pi }{22}\left(k\in Z\right)$

C. $x=\frac{\pi }{3}+\frac{k\pi }{18};x=\frac{\pi }{22}+\frac{k\pi }{22}\left(k\in Z\right)$

D. $x=\frac{k\pi }{3};x=\frac{\pi }{44}+\frac{k\pi }{44}\left(k\in Z\right)$

A. $\left|a\right|\ge 1$

B. $\left|a\right|>1$

C. $\left|a\right|=1$

D. $\left|a\right|\ne 1$

A. $\left\{\begin{array}{c}x=\frac{\pi }{6}+k2\pi \\ y=-\frac{\pi }{6}+k2\pi \end{array}\right.\left(k\in Z\right)$

B. $\left\{\begin{array}{c}x=\frac{2\pi }{3}+k2\pi \\ y=\frac{\pi }{3}-k2\pi \end{array}\right.\left(k\in Z\right)$

C. $\left\{\begin{array}{c}x=\frac{2\pi }{3}+k2\pi \\ y=\frac{\pi }{3}+k2\pi \end{array}\right.\left(k\in Z\right)$

D. $\left\{\begin{array}{c}x=\frac{\pi }{2}+k2\pi \\ y=\frac{\pi }{6}+k2\pi \end{array}\right.\left(k\in Z\right)$

A. $x=-\frac{\pi }{6}+k2\pi \left(k\in Z\right)$

B. $x=\frac{\pi }{6}+\frac{k2\pi }{3}\left(k\in Z\right)$

C. $x=-\frac{\pi }{6}+\frac{k2\pi }{3}\left(k\in Z\right)$

D. $x=\pm \frac{\pi }{6}+\frac{k2\pi }{3}\left(k\in Z\right)$

C. Vô nghiệm     

C. 2

A. $\frac{3\pi }{5}$

B. $\frac{29\pi }{30}$

C. $\frac{5\pi }{6}$

D. $\frac{23\pi }{30}$

A. $x=k\pi \left(k\in Z\right)$

B. $x=\frac{\pi }{2}+k\pi \left(k\in Z\right)$

C. $x=\frac{\pi }{6}+k2\pi \left(k\in Z\right)$

D. Tất cả đều đúng

A. $\iff \left[\begin{array}{c}x=\frac{\pi }{2}+k\pi \\ x=\frac{\pi }{6}+k\pi \end{array}\right.\left(k\in Z\right)$

B. $\left[\begin{array}{c}x=\frac{\pi }{4}+k\pi \\ x=\frac{\pi }{3}+k\pi \end{array}\right.\left(k\in Z\right)$

C. $\left[\begin{array}{c}x=\frac{\pi }{8}+k2\pi \\ x=\frac{\pi }{12}+k2\pi \end{array}\right.\left(k\in Z\right)$

D. $\left[\begin{array}{c}x=\frac{\pi }{8}+k\pi \\ x=\frac{\pi }{12}+k\pi \end{array}\right.\left(k\in Z\right)$

C. Hai nghiệm

A. $x=\frac{\pi }{9}+\frac{k2\pi }{3};\left(k\in Z\right)$

B. $x=\frac{\pi }{18}+\frac{k\pi }{6};\left(k\in Z\right)$

C. $x=\pm \frac{\pi }{6}+\frac{k\pi }{2};\left(k\in Z\right)$

D. $x=\frac{\pi }{18}+\frac{k\pi }{3};x=-\frac{\pi }{6}+\frac{k\pi }{2};\left(k\in Z\right)$

A. $x=-\frac{\pi }{4}+k\pi ;x=\frac{\pi }{6}+k2\pi ;x=\frac{5\pi }{6}+k2\pi ;x=-\frac{\pi }{2}+k2\pi \left(k\in Z\right)$

B. $x=\frac{\pi }{4}+k2\pi ;x=-\frac{\pi }{6}+k2\pi ;x=\frac{5\pi }{6}+k\pi ;x=-\frac{\pi }{2}+k\pi \left(k\in Z\right)$

C. $x=\pm \frac{\pi }{6}+k2\pi ;x=\frac{5\pi }{6}+k2\pi ;x=-\frac{\pi }{2}+k2\pi \left(k\in Z\right)$

D. $x=-\frac{\pi }{8}+k\pi ;x=\frac{\pi }{6}+k\pi ;x=-\frac{5\pi }{6}+\frac{k\pi }{6};x=-\frac{\pi }{2}+\frac{k\pi }{6}\left(k\in Z\right)$

A. $x=-\frac{\pi }{6}+\frac{k\pi }{2};x=\frac{\pi }{12}+\frac{k\pi }{2}\left(k\in Z\right)$

B. $x=\frac{\pi }{12}+\frac{k\pi }{4}\left(k\in Z\right)$

C. $x=\pm \frac{\pi }{6}+k\pi ;x=-\frac{\pi }{12}+\frac{k\pi }{2}\left(k\in Z\right)$

D. $x=\frac{\pi }{6}+k\pi ;x=-\frac{\pi }{12}+\frac{k\pi }{2}\left(k\in Z\right)$

A. $x=\pm \frac{\pi }{3}+k2\pi ;x=\frac{2\pi }{3}+k2\pi \left(k\in Z\right)$

B. $x=\frac{\pi }{4}+k\pi ;x=\frac{\pi }{6}+k\pi \left(k\in Z\right)$

C. $x=k\pi ;x=\frac{\pi }{3}+k2\pi ;x=\frac{2\pi }{3}+k2\pi \left(k\in Z\right)$

D. $x=\frac{\pi }{2}+k\pi ;x=\frac{\pi }{6}+\frac{k\pi }{3}\left(k\in Z\right)$

A. $x=\frac{\pi }{6}+k\pi ,k\in Z$

B. $x=-\frac{\pi }{12}+\frac{k\pi }{2},k\in Z$

C. $x=\frac{2\pi }{3}+k\pi ,k\in Z$

D. $x=\frac{k\pi }{12};x=\frac{2\pi }{3}+k\pi ,k\in Z$

A. $x=k\pi ;x=\frac{\pi }{6}+\frac{k\pi }{3},x=\frac{\pi }{12}+k\pi ,x=\frac{5\pi }{7}+k\pi$

B. $x=k2\pi ;x=\frac{\pi }{3}+\frac{k2\pi }{3},x=-\frac{\pi }{6}+k2\pi ,x=\frac{7\pi }{6}+k2\pi$

C. $x=k\pi ;x=\frac{\pi }{3}+\frac{k2\pi }{3},x=-\frac{\pi }{12}+k\pi ,x=\frac{5\pi }{12}+k\pi$

D. $x=k2\pi ;x=\frac{\pi }{6}+\frac{k2\pi }{3},x=\frac{\pi }{12}+k\pi ,x=\frac{7\pi }{12}+k\pi$

A. $x=\frac{\pi }{2}+k\pi ,x=\pm \frac{1}{5}\arccos \frac{1+\sqrt{17}}{8}+k\pi ,x=\pm \frac{1}{5}\arccos \frac{1-\sqrt{17}}{8}+k\pi$

B. $x=\pm \frac{\pi }{6}+k\pi$

C. $x=\pm \frac{1}{2}\arccos \frac{1+\sqrt{15}}{7}+k\pi ,x=\pm \frac{1}{2}\arccos \frac{1-\sqrt{15}}{7}+k\pi$

D. $x=\frac{\pi }{2}+k\pi ,x=\pm \frac{1}{2}\arccos \frac{1+\sqrt{17}}{8}+k\pi ,x=\pm \frac{1}{2}\arccos \frac{1-\sqrt{17}}{8}+k\pi$

A. $x=k\pi ,x=\frac{\pi }{3}+\frac{k2\pi }{3}$

B. $x=\pm \frac{\pi }{3}+\frac{k2\pi }{3}$

C. $x=\frac{\pi }{2}+k\pi ,x=-\frac{\pi }{3}+\frac{k2\pi }{3}$

D. $x=2k\pi ,x=\frac{\pi }{2}+\frac{k\pi }{3}$

C. 2

A. 9

C. 6

A. $m\ne \frac{1}{2}$

B. $m=\frac{1}{2}$

C. $\left\{\begin{array}{c}\frac{1}{3}<m<1\\ m\ne \frac{1}{2}\end{array}\right.$

D. $\frac{1}{3}<m<1$

A. $x=k\pi \left(k\in Z\right)$

B. $x=\frac{2\pi }{3}+2k\pi \left(k\in Z\right)$

C. $x=\frac{\pi }{3}+2k\pi \left(k\in Z\right)$

D. $x=\frac{k\pi }{3}\left(k\in Z\right)$

A. Vô nghiệm 

B. $x=\frac{\pi }{6}+\frac{k2\pi }{3}\left(k\in Z\right)$ hoặc $x=\frac{k2\pi }{3}\left(k\in Z\right)$

C. $x=\frac{\pi }{6}+k2\pi \left(k\in Z\right)$

D. $x=\frac{\pi }{6}+\frac{k\pi }{3}\left(k\in Z\right)$

A. $x=\frac{n\pi }{2};x=\frac{\pi }{20}+\frac{k\pi }{13}\left(k,n\in Z\right)$

B. $x=n\pi ;x=\frac{\pi }{20}+\frac{k\pi }{10}\left(k,n\in Z\right)$

C. $x=n\pi ;x=\frac{3\pi }{5}+\frac{2k\pi }{7}\left(k,n\in Z\right)$

D. $x=n\pi ;x=\frac{3\pi }{5}+\frac{7k\pi }{13}\left(k,n\in Z\right)$

C. 1

A. $\frac{24}{5}$

B. $\frac{28}{5}$

C. 5

D. $\frac{25}{8}$