Given the inequality:
$$\tan{\left(2 x \right)} \leq \frac{1}{2}$$
To solve this inequality, we must first solve the corresponding equation:
$$\tan{\left(2 x \right)} = \frac{1}{2}$$
Solve:
Given the equation
$$\tan{\left(2 x \right)} = \frac{1}{2}$$
- this is the simplest trigonometric equation
This equation is transformed to
$$2 x = \pi n + \operatorname{atan}{\left(\frac{1}{2} \right)}$$
Or
$$2 x = \pi n + \operatorname{atan}{\left(\frac{1}{2} \right)}$$
, where n - is a integer
Divide both parts of the equation by
$$2$$
$$x_{1} = \frac{\pi n}{2} + \frac{\operatorname{atan}{\left(\frac{1}{2} \right)}}{2}$$
$$x_{1} = \frac{\pi n}{2} + \frac{\operatorname{atan}{\left(\frac{1}{2} \right)}}{2}$$
This roots
$$x_{1} = \frac{\pi n}{2} + \frac{\operatorname{atan}{\left(\frac{1}{2} \right)}}{2}$$
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
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$\left(\frac{\pi n}{2} + \frac{\operatorname{atan}{\left(\frac{1}{2} \right)}}{2}\right) + - \frac{1}{10}$$
=
$$\frac{\pi n}{2} - \frac{1}{10} + \frac{\operatorname{atan}{\left(\frac{1}{2} \right)}}{2}$$
substitute to the expression
$$\tan{\left(2 x \right)} \leq \frac{1}{2}$$
$$\tan{\left(2 \left(\frac{\pi n}{2} - \frac{1}{10} + \frac{\operatorname{atan}{\left(\frac{1}{2} \right)}}{2}\right) \right)} \leq \frac{1}{2}$$
tan(-1/5 + pi*n + atan(1/2)) <= 1/2
the solution of our inequality is:
$$x \leq \frac{\pi n}{2} + \frac{\operatorname{atan}{\left(\frac{1}{2} \right)}}{2}$$
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