Mister Exam

Other calculators

sin2x<=√2\2 inequation

A inequation with variable

The solution

You have entered [src]
              ___
            \/ 2 
sin(2*x) <= -----
              2  
$$\sin{\left(2 x \right)} \leq \frac{\sqrt{2}}{2}$$
sin(2*x) <= sqrt(2)/2
Detail solution
Given the inequality:
$$\sin{\left(2 x \right)} \leq \frac{\sqrt{2}}{2}$$
To solve this inequality, we must first solve the corresponding equation:
$$\sin{\left(2 x \right)} = \frac{\sqrt{2}}{2}$$
Solve:
Given the equation
$$\sin{\left(2 x \right)} = \frac{\sqrt{2}}{2}$$
- this is the simplest trigonometric equation
This equation is transformed to
$$2 x = 2 \pi n + \operatorname{asin}{\left(\frac{\sqrt{2}}{2} \right)}$$
$$2 x = 2 \pi n - \operatorname{asin}{\left(\frac{\sqrt{2}}{2} \right)} + \pi$$
Or
$$2 x = 2 \pi n + \frac{\pi}{4}$$
$$2 x = 2 \pi n + \frac{3 \pi}{4}$$
, where n - is a integer
Divide both parts of the equation by
$$2$$
$$x_{1} = \pi n + \frac{\pi}{8}$$
$$x_{2} = \pi n + \frac{3 \pi}{8}$$
$$x_{1} = \pi n + \frac{\pi}{8}$$
$$x_{2} = \pi n + \frac{3 \pi}{8}$$
This roots
$$x_{1} = \pi n + \frac{\pi}{8}$$
$$x_{2} = \pi n + \frac{3 \pi}{8}$$
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
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$\left(\pi n + \frac{\pi}{8}\right) + - \frac{1}{10}$$
=
$$\pi n - \frac{1}{10} + \frac{\pi}{8}$$
substitute to the expression
$$\sin{\left(2 x \right)} \leq \frac{\sqrt{2}}{2}$$
$$\sin{\left(2 \left(\pi n - \frac{1}{10} + \frac{\pi}{8}\right) \right)} \leq \frac{\sqrt{2}}{2}$$
                            ___
   /  1   pi         \    \/ 2 
sin|- - + -- + 2*pi*n| <= -----
   \  5   4          /      2  
                          

one of the solutions of our inequality is:
$$x \leq \pi n + \frac{\pi}{8}$$
 _____           _____          
      \         /
-------•-------•-------
       x1      x2

Other solutions will get with the changeover to the next point
etc.
The answer:
$$x \leq \pi n + \frac{\pi}{8}$$
$$x \geq \pi n + \frac{3 \pi}{8}$$
Solving inequality on a graph
Rapid solution 2 [src]
        /   ___________\         /   ___________\     
        |  /       ___ |         |  /       ___ |     
        |\/  2 - \/ 2  |         |\/  2 + \/ 2  |     
[0, atan|--------------|] U [atan|--------------|, pi]
        |   ___________|         |   ___________|     
        |  /       ___ |         |  /       ___ |     
        \\/  2 + \/ 2  /         \\/  2 - \/ 2  /     
$$x\ in\ \left[0, \operatorname{atan}{\left(\frac{\sqrt{2 - \sqrt{2}}}{\sqrt{\sqrt{2} + 2}} \right)}\right] \cup \left[\operatorname{atan}{\left(\frac{\sqrt{\sqrt{2} + 2}}{\sqrt{2 - \sqrt{2}}} \right)}, \pi\right]$$
x in Union(Interval(0, atan(sqrt(2 - sqrt(2))/sqrt(sqrt(2) + 2))), Interval(atan(sqrt(sqrt(2) + 2)/sqrt(2 - sqrt(2))), pi))
Rapid solution [src]
  /   /                 /   ___________\\     /             /   ___________\     \\
  |   |                 |  /       ___ ||     |             |  /       ___ |     ||
  |   |                 |\/  2 - \/ 2  ||     |             |\/  2 + \/ 2  |     ||
Or|And|0 <= x, x <= atan|--------------||, And|x <= pi, atan|--------------| <= x||
  |   |                 |   ___________||     |             |   ___________|     ||
  |   |                 |  /       ___ ||     |             |  /       ___ |     ||
  \   \                 \\/  2 + \/ 2  //     \             \\/  2 - \/ 2  /     //
$$\left(0 \leq x \wedge x \leq \operatorname{atan}{\left(\frac{\sqrt{2 - \sqrt{2}}}{\sqrt{\sqrt{2} + 2}} \right)}\right) \vee \left(x \leq \pi \wedge \operatorname{atan}{\left(\frac{\sqrt{\sqrt{2} + 2}}{\sqrt{2 - \sqrt{2}}} \right)} \leq x\right)$$
((0 <= x)∧(x <= atan(sqrt(2 - sqrt(2))/sqrt(2 + sqrt(2)))))∨((x <= pi)∧(atan(sqrt(2 + sqrt(2))/sqrt(2 - sqrt(2))) <= x))