Given the inequality:
$$\sin{\left(\frac{x}{4} - 3 \right)} < \frac{1}{2}$$
To solve this inequality, we must first solve the corresponding equation:
$$\sin{\left(\frac{x}{4} - 3 \right)} = \frac{1}{2}$$
Solve:
Given the equation
$$\sin{\left(\frac{x}{4} - 3 \right)} = \frac{1}{2}$$
- this is the simplest trigonometric equation
This equation is transformed to
$$\frac{x}{4} - 3 = 2 \pi n + \operatorname{asin}{\left(\frac{1}{2} \right)}$$
$$\frac{x}{4} - 3 = 2 \pi n - \operatorname{asin}{\left(\frac{1}{2} \right)} + \pi$$
Or
$$\frac{x}{4} - 3 = 2 \pi n + \frac{\pi}{6}$$
$$\frac{x}{4} - 3 = 2 \pi n + \frac{5 \pi}{6}$$
, where n - is a integer
Move
$$-3$$
to right part of the equation
with the opposite sign, in total:
$$\frac{x}{4} = 2 \pi n + \frac{\pi}{6} + 3$$
$$\frac{x}{4} = 2 \pi n + \frac{5 \pi}{6} + 3$$
Divide both parts of the equation by
$$\frac{1}{4}$$
$$x_{1} = 8 \pi n + \frac{2 \pi}{3} + 12$$
$$x_{2} = 8 \pi n + \frac{10 \pi}{3} + 12$$
$$x_{1} = 8 \pi n + \frac{2 \pi}{3} + 12$$
$$x_{2} = 8 \pi n + \frac{10 \pi}{3} + 12$$
This roots
$$x_{1} = 8 \pi n + \frac{2 \pi}{3} + 12$$
$$x_{2} = 8 \pi n + \frac{10 \pi}{3} + 12$$
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
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$\left(8 \pi n + \frac{2 \pi}{3} + 12\right) + - \frac{1}{10}$$
=
$$8 \pi n + \frac{2 \pi}{3} + \frac{119}{10}$$
substitute to the expression
$$\sin{\left(\frac{x}{4} - 3 \right)} < \frac{1}{2}$$
$$\sin{\left(\frac{8 \pi n + \frac{2 \pi}{3} + \frac{119}{10}}{4} - 3 \right)} < \frac{1}{2}$$
/ 1 pi \
sin|- -- + -- + 2*pi*n| < 1/2
\ 40 6 /
one of the solutions of our inequality is:
$$x < 8 \pi n + \frac{2 \pi}{3} + 12$$
_____ _____
\ /
-------ο-------ο-------
x1 x2
Other solutions will get with the changeover to the next point
etc.
The answer:
$$x < 8 \pi n + \frac{2 \pi}{3} + 12$$
$$x > 8 \pi n + \frac{10 \pi}{3} + 12$$