\(3{\cos ^4}x - 4{\sin ^2}x{\cos ^2}x + {\sin ^4}x = 0.\)
A.\(\left[ \begin{array}{l}x = \frac{{2\pi }}{3} + k2\pi \\x = \frac{\pi }{3} + k2\pi \\x = \frac{\pi }{4} + k2\pi \\x = \frac{{3\pi }}{4} + k2\pi \end{array} \right.\,\,\,\,\left( {k \in \mathbb{Z}} \right)\)
B.\(\left[ \begin{array}{l}x = \frac{{2\pi }}{3} + k\pi \\x = \frac{\pi }{3} + k\pi \\x = - \frac{\pi }{4} + k\pi \\x = \frac{{5\pi }}{4} + k\pi \end{array} \right.\,\,\,\,\left( {k \in \mathbb{Z}} \right)\)
C.\(\left[ \begin{array}{l}x = \frac{{2\pi }}{3} + k2\pi \\x = \frac{\pi }{3} + k2\pi \\x = - \frac{\pi }{4} + k2\pi \\x = \frac{{5\pi }}{4} + k2\pi \end{array} \right.\,\,\,\,\left( {k \in \mathbb{Z}} \right)\)
D.\(\left[ \begin{array}{l}x = \frac{{2\pi }}{3} + k\pi \\x = \frac{\pi }{3} + k\pi \\x = \frac{\pi }{4} + k\pi \\x = \frac{{3\pi }}{4} + k\pi \end{array} \right.\,\,\,\,\left( {k \in \mathbb{Z}} \right)\)
A.\(\left[ \begin{array}{l}x = \frac{{2\pi }}{3} + k2\pi \\x = \frac{\pi }{3} + k2\pi \\x = \frac{\pi }{4} + k2\pi \\x = \frac{{3\pi }}{4} + k2\pi \end{array} \right.\,\,\,\,\left( {k \in \mathbb{Z}} \right)\)
B.\(\left[ \begin{array}{l}x = \frac{{2\pi }}{3} + k\pi \\x = \frac{\pi }{3} + k\pi \\x = - \frac{\pi }{4} + k\pi \\x = \frac{{5\pi }}{4} + k\pi \end{array} \right.\,\,\,\,\left( {k \in \mathbb{Z}} \right)\)
C.\(\left[ \begin{array}{l}x = \frac{{2\pi }}{3} + k2\pi \\x = \frac{\pi }{3} + k2\pi \\x = - \frac{\pi }{4} + k2\pi \\x = \frac{{5\pi }}{4} + k2\pi \end{array} \right.\,\,\,\,\left( {k \in \mathbb{Z}} \right)\)
D.\(\left[ \begin{array}{l}x = \frac{{2\pi }}{3} + k\pi \\x = \frac{\pi }{3} + k\pi \\x = \frac{\pi }{4} + k\pi \\x = \frac{{3\pi }}{4} + k\pi \end{array} \right.\,\,\,\,\left( {k \in \mathbb{Z}} \right)\)
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