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cost>−0.5 inequation

A inequation with variable

The solution

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cos(t) > -1/2
$$\cos{\left(t \right)} > - \frac{1}{2}$$
cos(t) > -1/2
Detail solution
Given the inequality:
$$\cos{\left(t \right)} > - \frac{1}{2}$$
To solve this inequality, we must first solve the corresponding equation:
$$\cos{\left(t \right)} = - \frac{1}{2}$$
Solve:
Given the equation
$$\cos{\left(t \right)} = - \frac{1}{2}$$
- this is the simplest trigonometric equation
This equation is transformed to
$$t = \pi n + \operatorname{acos}{\left(- \frac{1}{2} \right)}$$
$$t = \pi n - \pi + \operatorname{acos}{\left(- \frac{1}{2} \right)}$$
Or
$$t = \pi n + \frac{2 \pi}{3}$$
$$t = \pi n - \frac{\pi}{3}$$
, where n - is a integer
$$t_{1} = \pi n + \frac{2 \pi}{3}$$
$$t_{2} = \pi n - \frac{\pi}{3}$$
$$t_{1} = \pi n + \frac{2 \pi}{3}$$
$$t_{2} = \pi n - \frac{\pi}{3}$$
This roots
$$t_{1} = \pi n + \frac{2 \pi}{3}$$
$$t_{2} = \pi n - \frac{\pi}{3}$$
is the points with change the sign of the inequality expression.
First define with the sign to the leftmost point:
$$t_{0} < t_{1}$$
For example, let's take the point
$$t_{0} = t_{1} - \frac{1}{10}$$
=
$$\left(\pi n + \frac{2 \pi}{3}\right) + - \frac{1}{10}$$
=
$$\pi n - \frac{1}{10} + \frac{2 \pi}{3}$$
substitute to the expression
$$\cos{\left(t \right)} > - \frac{1}{2}$$
$$\cos{\left(\pi n - \frac{1}{10} + \frac{2 \pi}{3} \right)} > - \frac{1}{2}$$
    /  1    pi       \       
-sin|- -- + -- + pi*n| > -1/2
    \  10   6        /       

one of the solutions of our inequality is:
$$t < \pi n + \frac{2 \pi}{3}$$
 _____           _____          
      \         /
-------ο-------ο-------
       t1      t2

Other solutions will get with the changeover to the next point
etc.
The answer:
$$t < \pi n + \frac{2 \pi}{3}$$
$$t > \pi n - \frac{\pi}{3}$$
Solving inequality on a graph
Rapid solution 2 [src]
    2*pi     4*pi       
[0, ----) U (----, 2*pi]
     3        3         
$$t\ in\ \left[0, \frac{2 \pi}{3}\right) \cup \left(\frac{4 \pi}{3}, 2 \pi\right]$$
t in Union(Interval.Ropen(0, 2*pi/3), Interval.Lopen(4*pi/3, 2*pi))
Rapid solution [src]
  /   /            2*pi\     /           4*pi    \\
Or|And|0 <= t, t < ----|, And|t <= 2*pi, ---- < t||
  \   \             3  /     \            3      //
$$\left(0 \leq t \wedge t < \frac{2 \pi}{3}\right) \vee \left(t \leq 2 \pi \wedge \frac{4 \pi}{3} < t\right)$$
((0 <= t)∧(t < 2*pi/3))∨((t <= 2*pi)∧(4*pi/3 < t))