Given the inequality:
$$\tan{\left(3 x \right)} < 1$$
To solve this inequality, we must first solve the corresponding equation:
$$\tan{\left(3 x \right)} = 1$$
Solve:
Given the equation
$$\tan{\left(3 x \right)} = 1$$
- this is the simplest trigonometric equation
This equation is transformed to
$$3 x = \pi n + \operatorname{atan}{\left(1 \right)}$$
Or
$$3 x = \pi n + \frac{\pi}{4}$$
, where n - is a integer
Divide both parts of the equation by
$$3$$
$$x_{1} = \frac{\pi n}{3} + \frac{\pi}{12}$$
$$x_{1} = \frac{\pi n}{3} + \frac{\pi}{12}$$
This roots
$$x_{1} = \frac{\pi n}{3} + \frac{\pi}{12}$$
is the points with change the sign of the inequality expression.
First define with the sign to the leftmost point:
$$x_{0} < x_{1}$$
For example, let's take the point
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$\left(\frac{\pi n}{3} + \frac{\pi}{12}\right) + - \frac{1}{10}$$
=
$$\frac{\pi n}{3} - \frac{1}{10} + \frac{\pi}{12}$$
substitute to the expression
$$\tan{\left(3 x \right)} < 1$$
$$\tan{\left(3 \left(\frac{\pi n}{3} - \frac{1}{10} + \frac{\pi}{12}\right) \right)} < 1$$
/ 3 pi \
tan|- -- + -- + pi*n| < 1
\ 10 4 /
the solution of our inequality is:
$$x < \frac{\pi n}{3} + \frac{\pi}{12}$$
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