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sinx<-1/4 inequation

A inequation with variable

The solution

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sin(x) < -1/4
$$\sin{\left(x \right)} < - \frac{1}{4}$$
sin(x) < -1/4
Detail solution
Given the inequality:
$$\sin{\left(x \right)} < - \frac{1}{4}$$
To solve this inequality, we must first solve the corresponding equation:
$$\sin{\left(x \right)} = - \frac{1}{4}$$
Solve:
Given the equation
$$\sin{\left(x \right)} = - \frac{1}{4}$$
- this is the simplest trigonometric equation
This equation is transformed to
$$x = 2 \pi n + \operatorname{asin}{\left(- \frac{1}{4} \right)}$$
$$x = 2 \pi n - \operatorname{asin}{\left(- \frac{1}{4} \right)} + \pi$$
Or
$$x = 2 \pi n - \operatorname{asin}{\left(\frac{1}{4} \right)}$$
$$x = 2 \pi n + \operatorname{asin}{\left(\frac{1}{4} \right)} + \pi$$
, where n - is a integer
$$x_{1} = 2 \pi n - \operatorname{asin}{\left(\frac{1}{4} \right)}$$
$$x_{2} = 2 \pi n + \operatorname{asin}{\left(\frac{1}{4} \right)} + \pi$$
$$x_{1} = 2 \pi n - \operatorname{asin}{\left(\frac{1}{4} \right)}$$
$$x_{2} = 2 \pi n + \operatorname{asin}{\left(\frac{1}{4} \right)} + \pi$$
This roots
$$x_{1} = 2 \pi n - \operatorname{asin}{\left(\frac{1}{4} \right)}$$
$$x_{2} = 2 \pi n + \operatorname{asin}{\left(\frac{1}{4} \right)} + \pi$$
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
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$\left(2 \pi n - \operatorname{asin}{\left(\frac{1}{4} \right)}\right) + - \frac{1}{10}$$
=
$$2 \pi n - \operatorname{asin}{\left(\frac{1}{4} \right)} - \frac{1}{10}$$
substitute to the expression
$$\sin{\left(x \right)} < - \frac{1}{4}$$
$$\sin{\left(2 \pi n - \operatorname{asin}{\left(\frac{1}{4} \right)} - \frac{1}{10} \right)} < - \frac{1}{4}$$
-sin(1/10 - 2*pi*n + asin(1/4)) < -1/4

one of the solutions of our inequality is:
$$x < 2 \pi n - \operatorname{asin}{\left(\frac{1}{4} \right)}$$
 _____           _____          
      \         /
-------ο-------ο-------
       x1      x2

Other solutions will get with the changeover to the next point
etc.
The answer:
$$x < 2 \pi n - \operatorname{asin}{\left(\frac{1}{4} \right)}$$
$$x > 2 \pi n + \operatorname{asin}{\left(\frac{1}{4} \right)} + \pi$$
Solving inequality on a graph
Rapid solution [src]
   /          /  ____\                  /  ____\    \
   |          |\/ 15 |                  |\/ 15 |    |
And|x < - atan|------| + 2*pi, pi + atan|------| < x|
   \          \  15  /                  \  15  /    /
$$x < - \operatorname{atan}{\left(\frac{\sqrt{15}}{15} \right)} + 2 \pi \wedge \operatorname{atan}{\left(\frac{\sqrt{15}}{15} \right)} + \pi < x$$
(pi + atan(sqrt(15)/15) < x)∧(x < -atan(sqrt(15)/15) + 2*pi)
Rapid solution 2 [src]
          /  ____\        /  ____\        
          |\/ 15 |        |\/ 15 |        
(pi + atan|------|, - atan|------| + 2*pi)
          \  15  /        \  15  /        
$$x\ in\ \left(\operatorname{atan}{\left(\frac{\sqrt{15}}{15} \right)} + \pi, - \operatorname{atan}{\left(\frac{\sqrt{15}}{15} \right)} + 2 \pi\right)$$
x in Interval.open(atan(sqrt(15)/15) + pi, -atan(sqrt(15)/15) + 2*pi)