Đáp án:
$\begin{array}{l}
11){\cot ^3}2x = 1\\
\Rightarrow \cot 2x = 1\\
\Rightarrow 2x = \frac{\pi }{4} + k\pi \\
\Rightarrow x = \frac{\pi }{8} + \frac{{k\pi }}{2}\\
12)\\
\tan \left( {4{x^0} + 2} \right) = 3\\
\Rightarrow 4{x^0} + 2 = {72^0} + k{.180^0}\\
\Rightarrow x = 17,{5^0} + k{.45^0}\\
13)\\
\sqrt 3 \tan 3{x^0} - \sqrt 3 = 0\\
\Rightarrow \tan 3{x^0} = 1\\
\Rightarrow 3{x^0} = {45^0} + k{.180^0}\\
\Rightarrow x = {15^0} + k{.60^0}\\
14){\tan ^2}x - 3 = 0\\
\Rightarrow {\tan ^2}x = 3\\
\Rightarrow \left[ \begin{array}{l}
\tan x = \sqrt 3 \\
\tan x = - \sqrt 3
\end{array} \right.\\
\Rightarrow \left[ \begin{array}{l}
x = \frac{\pi }{3} + k\pi \\
x = - \frac{\pi }{3} + k\pi
\end{array} \right.\\
15)\tan \left( {3{x^0} + {{12}^0}} \right) = \tan {60^0}\\
\Rightarrow 3{x^0} + {12^0} = {60^0} + k{.180^0}\\
\Rightarrow x = {16^0} + k{.60^0}
\end{array}$
