Given the inequality:
$$\cot{\left(x + \frac{\pi}{6} \right)} \geq \frac{\sqrt{3}}{3}$$
To solve this inequality, we must first solve the corresponding equation:
$$\cot{\left(x + \frac{\pi}{6} \right)} = \frac{\sqrt{3}}{3}$$
Solve:
$$x_{1} = \frac{\pi}{6}$$
$$x_{1} = \frac{\pi}{6}$$
This roots
$$x_{1} = \frac{\pi}{6}$$
is the points with change the sign of the inequality expression.
First define with the sign to the leftmost point:
$$x_{0} \leq x_{1}$$
For example, let's take the point
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- \frac{1}{10} + \frac{\pi}{6}$$
=
$$- \frac{1}{10} + \frac{\pi}{6}$$
substitute to the expression
$$\cot{\left(x + \frac{\pi}{6} \right)} \geq \frac{\sqrt{3}}{3}$$
$$\cot{\left(\left(- \frac{1}{10} + \frac{\pi}{6}\right) + \frac{\pi}{6} \right)} \geq \frac{\sqrt{3}}{3}$$
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/1 pi\ \/ 3
tan|-- + --| >= -----
\10 6 / 3
the solution of our inequality is:
$$x \leq \frac{\pi}{6}$$
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