Phương trình \(\cos 11x\cos 3x = \cos 17x\cos 9x\) có nghiệm là:

\(\left[ \begin{array}{l}x = \dfrac{\pi }{6} + k2\pi \\x = \dfrac{{5\pi }}{6} + k2\pi \end{array} \right.\left( {k \in Z} \right)\)          

\(\left[ \begin{array}{l}x = \dfrac{\pi }{6} + k2\pi \\x =  - \dfrac{\pi }{6} + k2\pi \end{array} \right.\left( {k \in Z} \right)\)

\(\left[ \begin{array}{l}x = \dfrac{\pi }{3} + k2\pi \\x = \dfrac{{2\pi }}{3} + k2\pi \end{array} \right.\left( {k \in Z} \right)\)          

\(\left[ \begin{array}{l}x = \dfrac{\pi }{3} + k2\pi \\x =  - \dfrac{\pi }{3} + k2\pi \end{array} \right.\left( {k \in Z} \right)\)

$0$ 

$1$ 

$2$ 

vô số

\(m = 1\)

Không có m

\(m = 0\)

Với mọi m

$A'\left( { - 2;7} \right)$ 

\(A'\left( { - \dfrac{{24}}{5};\dfrac{7}{5}} \right)\) 

\(A'\left( {\dfrac{{24}}{5};\dfrac{7}{5}} \right)\) 

\(A'\left( {12;\dfrac{7}{5}} \right)\) 

$\left[ \begin{array}{l}x = \dfrac{\pi }{3} + k\pi \\x = \dfrac{\pi }{6} + k\pi \end{array} \right.\,\,\left( {k \in Z} \right)$

$\left[ \begin{array}{l}x = \dfrac{\pi }{3} + k2\pi \\x = \dfrac{\pi }{6} + k2\pi \end{array} \right.\,\,\left( {k \in Z} \right)$

$\left[ \begin{array}{l}x =  - \dfrac{\pi }{3} + k\pi \\x =  - \dfrac{\pi }{6} + k\pi \end{array} \right.\,\,\left( {k \in Z} \right)$

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

\(R\backslash \left\{ {k\pi ,k \in Z} \right\}\)

\(R\backslash \left\{ {\dfrac{{k\pi }}{2},k \in Z} \right\}\)

\(R\backslash \left\{ {\dfrac{\pi }{2} + k\pi ,k \in Z} \right\}\)

\(R\)

Hàm số không tuần hoàn

\({T_0} = 2\pi \)

\({T_0} = \pi \)

\({T_0} = 4{\pi ^2}\)