Mister Exam

2sin(2x)<=1 inequation

A inequation with variable

The solution

You have entered [src]
2*sin(2*x) <= 1
$$2 \sin{\left(2 x \right)} \leq 1$$
2*sin(2*x) <= 1
Detail solution
Given the inequality:
$$2 \sin{\left(2 x \right)} \leq 1$$
To solve this inequality, we must first solve the corresponding equation:
$$2 \sin{\left(2 x \right)} = 1$$
Solve:
Given the equation
$$2 \sin{\left(2 x \right)} = 1$$
- this is the simplest trigonometric equation
Divide both parts of the equation by 2

The equation is transformed to
$$\sin{\left(2 x \right)} = \frac{1}{2}$$
This equation is transformed to
$$2 x = 2 \pi n + \operatorname{asin}{\left(\frac{1}{2} \right)}$$
$$2 x = 2 \pi n - \operatorname{asin}{\left(\frac{1}{2} \right)} + \pi$$
Or
$$2 x = 2 \pi n + \frac{\pi}{6}$$
$$2 x = 2 \pi n + \frac{5 \pi}{6}$$
, where n - is a integer
Divide both parts of the equation by
$$2$$
$$x_{1} = \pi n + \frac{\pi}{12}$$
$$x_{2} = \pi n + \frac{5 \pi}{12}$$
$$x_{1} = \pi n + \frac{\pi}{12}$$
$$x_{2} = \pi n + \frac{5 \pi}{12}$$
This roots
$$x_{1} = \pi n + \frac{\pi}{12}$$
$$x_{2} = \pi n + \frac{5 \pi}{12}$$
is the points with change the sign of the inequality expression.
First define with the sign to the leftmost point:
$$x_{0} \leq x_{1}$$
For example, let's take the point
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$\left(\pi n + \frac{\pi}{12}\right) + - \frac{1}{10}$$
=
$$\pi n - \frac{1}{10} + \frac{\pi}{12}$$
substitute to the expression
$$2 \sin{\left(2 x \right)} \leq 1$$
$$2 \sin{\left(2 \left(\pi n - \frac{1}{10} + \frac{\pi}{12}\right) \right)} \leq 1$$
     /  1   pi         \     
2*sin|- - + -- + 2*pi*n| <= 1
     \  5   6          /     

one of the solutions of our inequality is:
$$x \leq \pi n + \frac{\pi}{12}$$
 _____           _____          
      \         /
-------•-------•-------
       x1      x2

Other solutions will get with the changeover to the next point
etc.
The answer:
$$x \leq \pi n + \frac{\pi}{12}$$
$$x \geq \pi n + \frac{5 \pi}{12}$$
Solving inequality on a graph
Rapid solution [src]
  /   /                 /  ___     ___\\     /             /  ___     ___\     \\
  |   |                 |\/ 6  - \/ 2 ||     |             |\/ 2  + \/ 6 |     ||
Or|And|0 <= x, x <= atan|-------------||, And|x <= pi, atan|-------------| <= x||
  |   |                 |  ___     ___||     |             |  ___     ___|     ||
  \   \                 \\/ 2  + \/ 6 //     \             \\/ 6  - \/ 2 /     //
$$\left(0 \leq x \wedge x \leq \operatorname{atan}{\left(\frac{- \sqrt{2} + \sqrt{6}}{\sqrt{2} + \sqrt{6}} \right)}\right) \vee \left(x \leq \pi \wedge \operatorname{atan}{\left(\frac{\sqrt{2} + \sqrt{6}}{- \sqrt{2} + \sqrt{6}} \right)} \leq x\right)$$
((0 <= x)∧(x <= atan((sqrt(6) - sqrt(2))/(sqrt(2) + sqrt(6)))))∨((x <= pi)∧(atan((sqrt(2) + sqrt(6))/(sqrt(6) - sqrt(2))) <= x))
Rapid solution 2 [src]
         /  ___     ___\          /  ___     ___\     
         |\/ 2  - \/ 6 |          |\/ 2  + \/ 6 |     
[0, -atan|-------------|] U [-atan|-------------|, pi]
         |  ___     ___|          |  ___     ___|     
         \\/ 2  + \/ 6 /          \\/ 2  - \/ 6 /     
$$x\ in\ \left[0, - \operatorname{atan}{\left(\frac{- \sqrt{6} + \sqrt{2}}{\sqrt{2} + \sqrt{6}} \right)}\right] \cup \left[- \operatorname{atan}{\left(\frac{\sqrt{2} + \sqrt{6}}{- \sqrt{6} + \sqrt{2}} \right)}, \pi\right]$$
x in Union(Interval(0, -atan((-sqrt(6) + sqrt(2))/(sqrt(2) + sqrt(6)))), Interval(-atan((sqrt(2) + sqrt(6))/(-sqrt(6) + sqrt(2))), pi))