Given the inequality:
$$\frac{\cos{\left(x \right)}}{3} < \frac{\sqrt{3}}{2}$$
To solve this inequality, we must first solve the corresponding equation:
$$\frac{\cos{\left(x \right)}}{3} = \frac{\sqrt{3}}{2}$$
Solve:
Given the equation
$$\frac{\cos{\left(x \right)}}{3} = \frac{\sqrt{3}}{2}$$
- this is the simplest trigonometric equation
Divide both parts of the equation by 1/3
The equation is transformed to
$$\cos{\left(x \right)} = \frac{3 \sqrt{3}}{2}$$
As right part of the equation
modulo =
True
but cos
can no be more than 1 or less than -1
so the solution of the equation d'not exist.
$$x_{1} = 2 \pi - \operatorname{acos}{\left(\frac{3 \sqrt{3}}{2} \right)}$$
$$x_{2} = \operatorname{acos}{\left(\frac{3 \sqrt{3}}{2} \right)}$$
Exclude the complex solutions:
This equation has no roots,
this inequality is executed for any x value or has no solutions
check it
subtitute random point x, for example
x0 = 0
$$\frac{\cos{\left(0 \right)}}{3} < \frac{\sqrt{3}}{2}$$
___
\/ 3
1/3 < -----
2
so the inequality is always executed