Mister Exam

ctg(2x)≤√3 inequation

A inequation with variable

The solution

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cot(2*x) <= \/ 3 
$$\cot{\left(2 x \right)} \leq \sqrt{3}$$
cot(2*x) <= sqrt(3)
Detail solution
Given the inequality:
$$\cot{\left(2 x \right)} \leq \sqrt{3}$$
To solve this inequality, we must first solve the corresponding equation:
$$\cot{\left(2 x \right)} = \sqrt{3}$$
Solve:
Given the equation
$$\cot{\left(2 x \right)} = \sqrt{3}$$
transform
$$\cot{\left(2 x \right)} - \sqrt{3} - 1 = 0$$
$$\cot{\left(2 x \right)} - \sqrt{3} - 1 = 0$$
Do replacement
$$w = \cot{\left(2 x \right)}$$
Expand brackets in the left part
-1 + w - sqrt3 = 0

Move free summands (without w)
from left part to right part, we given:
$$w - \sqrt{3} = 1$$
Divide both parts of the equation by (w - sqrt(3))/w
w = 1 / ((w - sqrt(3))/w)

We get the answer: w = 1 + sqrt(3)
do backward replacement
$$\cot{\left(2 x \right)} = w$$
substitute w:
$$x_{1} = \frac{\pi}{12}$$
$$x_{1} = \frac{\pi}{12}$$
This roots
$$x_{1} = \frac{\pi}{12}$$
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
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- \frac{1}{10} + \frac{\pi}{12}$$
=
$$- \frac{1}{10} + \frac{\pi}{12}$$
substitute to the expression
$$\cot{\left(2 x \right)} \leq \sqrt{3}$$
$$\cot{\left(2 \left(- \frac{1}{10} + \frac{\pi}{12}\right) \right)} \leq \sqrt{3}$$
   /1   pi\      ___
tan|- + --| <= \/ 3 
   \5   3 /    

but
   /1   pi\      ___
tan|- + --| >= \/ 3 
   \5   3 /    

Then
$$x \leq \frac{\pi}{12}$$
no execute
the solution of our inequality is:
$$x \geq \frac{\pi}{12}$$
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Rapid solution [src]
   /     /  ___     ___\             \
   |     |\/ 2  - \/ 6 |           pi|
And|-atan|-------------| <= x, x < --|
   |     |  ___     ___|           2 |
   \     \\/ 2  + \/ 6 /             /
$$- \operatorname{atan}{\left(\frac{- \sqrt{6} + \sqrt{2}}{\sqrt{2} + \sqrt{6}} \right)} \leq x \wedge x < \frac{\pi}{2}$$
(x < pi/2)∧(-atan((sqrt(2) - sqrt(6))/(sqrt(2) + sqrt(6))) <= x)
Rapid solution 2 [src]
      /  ___     ___\     
      |\/ 2  - \/ 6 |  pi 
[-atan|-------------|, --)
      |  ___     ___|  2  
      \\/ 2  + \/ 6 /     
$$x\ in\ \left[- \operatorname{atan}{\left(\frac{- \sqrt{6} + \sqrt{2}}{\sqrt{2} + \sqrt{6}} \right)}, \frac{\pi}{2}\right)$$
x in Interval.Ropen(-atan((-sqrt(6) + sqrt(2))/(sqrt(2) + sqrt(6))), pi/2)