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3sin^2(2x)+7cos(2x)-3>=0

3sin^2(2x)+7cos(2x)-3>=0 inequation

A inequation with variable

The solution

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     2                           
3*sin (2*x) + 7*cos(2*x) - 3 >= 0
$$3 \sin^{2}{\left(2 x \right)} + 7 \cos{\left(2 x \right)} - 3 \geq 0$$
3*sin(2*x)^2 + 7*cos(2*x) - 1*3 >= 0
Detail solution
Given the inequality:
$$3 \sin^{2}{\left(2 x \right)} + 7 \cos{\left(2 x \right)} - 3 \geq 0$$
To solve this inequality, we must first solve the corresponding equation:
$$3 \sin^{2}{\left(2 x \right)} + 7 \cos{\left(2 x \right)} - 3 = 0$$
Solve:
$$x_{1} = - \frac{\pi}{4}$$
$$x_{2} = \frac{\pi}{4}$$
$$x_{3} = - i \operatorname{atanh}{\left(\frac{\sqrt{10}}{5} \right)}$$
$$x_{4} = i \operatorname{atanh}{\left(\frac{\sqrt{10}}{5} \right)}$$
Exclude the complex solutions:
$$x_{1} = - \frac{\pi}{4}$$
$$x_{2} = \frac{\pi}{4}$$
This roots
$$x_{1} = - \frac{\pi}{4}$$
$$x_{2} = \frac{\pi}{4}$$
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
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- \frac{\pi}{4} - \frac{1}{10}$$
=
$$- \frac{\pi}{4} - \frac{1}{10}$$
substitute to the expression
$$3 \sin^{2}{\left(2 x \right)} + 7 \cos{\left(2 x \right)} - 3 \geq 0$$
$$\left(-1\right) 3 + 7 \cos{\left(2 \left(- \frac{\pi}{4} - \frac{1}{10}\right) \right)} + 3 \sin^{2}{\left(2 \left(- \frac{\pi}{4} - \frac{1}{10}\right) \right)} \geq 0$$
                       2          
-3 - 7*sin(1/5) + 3*cos (1/5) >= 0
     

but
                       2         
-3 - 7*sin(1/5) + 3*cos (1/5) < 0
    

Then
$$x \leq - \frac{\pi}{4}$$
no execute
one of the solutions of our inequality is:
$$x \geq - \frac{\pi}{4} \wedge x \leq \frac{\pi}{4}$$
         _____  
        /     \  
-------•-------•-------
       x_1      x_2
Solving inequality on a graph
Rapid solution [src]
  /   /             pi\     /3*pi            5*pi\     /7*pi               \\
Or|And|0 <= x, x <= --|, And|---- <= x, x <= ----|, And|---- <= x, x < 2*pi||
  \   \             4 /     \ 4               4  /     \ 4                 //
$$\left(0 \leq x \wedge x \leq \frac{\pi}{4}\right) \vee \left(\frac{3 \pi}{4} \leq x \wedge x \leq \frac{5 \pi}{4}\right) \vee \left(\frac{7 \pi}{4} \leq x \wedge x < 2 \pi\right)$$
((0 <= x)∧(x <= pi/4))∨((3*pi/4 <= x)∧(x <= 5*pi/4))∨((7*pi/4 <= x)∧(x < 2*pi))
Rapid solution 2 [src]
    pi     3*pi  5*pi     7*pi       
[0, --] U [----, ----] U [----, 2*pi)
    4       4     4        4         
$$x\ in\ \left[0, \frac{\pi}{4}\right] \cup \left[\frac{3 \pi}{4}, \frac{5 \pi}{4}\right] \cup \left[\frac{7 \pi}{4}, 2 \pi\right)$$
x in Union(Interval(0, pi/4), Interval(3*pi/4, 5*pi/4), Interval.Ropen(7*pi/4, 2*pi))
The graph
3sin^2(2x)+7cos(2x)-3>=0 inequation