Given the inequality:
$$\tan{\left(\frac{x}{7} - \frac{5 \pi}{6} \right)} < -3$$
To solve this inequality, we must first solve the corresponding equation:
$$\tan{\left(\frac{x}{7} - \frac{5 \pi}{6} \right)} = -3$$
Solve:
Given the equation
$$\tan{\left(\frac{x}{7} - \frac{5 \pi}{6} \right)} = -3$$
- this is the simplest trigonometric equation
This equation is transformed to
$$\frac{x}{7} + \frac{\pi}{6} = \pi n + \operatorname{atan}{\left(-3 \right)}$$
Or
$$\frac{x}{7} + \frac{\pi}{6} = \pi n - \operatorname{atan}{\left(3 \right)}$$
, where n - is a integer
Move
$$\frac{\pi}{6}$$
to right part of the equation with the opposite sign, in total:
$$\frac{x}{7} = \pi n - \operatorname{atan}{\left(3 \right)} - \frac{\pi}{6}$$
Divide both parts of the equation by
$$\frac{1}{7}$$
get the intermediate answer:
$$x = 7 \pi n - 7 \operatorname{atan}{\left(3 \right)} - \frac{7 \pi}{6}$$
$$x_{1} = 7 \pi n - 7 \operatorname{atan}{\left(3 \right)} - \frac{7 \pi}{6}$$
$$x_{1} = 7 \pi n - 7 \operatorname{atan}{\left(3 \right)} - \frac{7 \pi}{6}$$
This roots
$$x_{1} = 7 \pi n - 7 \operatorname{atan}{\left(3 \right)} - \frac{7 \pi}{6}$$
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
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$\left(7 \pi n - 7 \operatorname{atan}{\left(3 \right)} - \frac{7 \pi}{6}\right) - \frac{1}{10}$$
=
$$7 \pi n - 7 \operatorname{atan}{\left(3 \right)} - \frac{7 \pi}{6} - \frac{1}{10}$$
substitute to the expression
$$\tan{\left(\frac{x}{7} - \frac{5 \pi}{6} \right)} < -3$$
$$\tan{\left(\frac{7 \pi n - 7 \operatorname{atan}{\left(3 \right)} - \frac{7 \pi}{6} - \frac{1}{10}}{7} - \frac{5 \pi}{6} \right)} < -3$$
-tan(1/70 + atan(3)) < -3
the solution of our inequality is:
$$x < 7 \pi n - 7 \operatorname{atan}{\left(3 \right)} - \frac{7 \pi}{6}$$
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