Math Problem Statement

Find all x values in the interval [0, 2π] that satisfies: 2 cos(x) − 1 > 0

Solution

To solve the inequality 2cos(x)1>02 \cos(x) - 1 > 0 for xx in the interval [0,2π][0, 2\pi], follow these steps:

Step 1: Solve the inequality

2cos(x)1>02 \cos(x) - 1 > 0 Add 1 to both sides: 2cos(x)>12 \cos(x) > 1 Divide by 2: cos(x)>12\cos(x) > \frac{1}{2}

Step 2: Determine the values of xx where cos(x)>12\cos(x) > \frac{1}{2}

The cosine function is positive in the first and fourth quadrants. Specifically, cos(x)>12\cos(x) > \frac{1}{2} when: x(π3,π3)(5π3,7π3)x \in \left( -\frac{\pi}{3}, \frac{\pi}{3} \right) \cup \left( \frac{5\pi}{3}, \frac{7\pi}{3} \right)

Step 3: Adjust the intervals to match the given interval [0,2π][0, 2\pi]

We need to find the xx values within the interval [0,2π][0, 2\pi]. The relevant portions of the solution are: x[0,π3)(5π3,2π]x \in \left[ 0, \frac{\pi}{3} \right) \cup \left( \frac{5\pi}{3}, 2\pi \right]

Final Answer

The values of xx that satisfy 2cos(x)1>02 \cos(x) - 1 > 0 in the interval [0,2π][0, 2\pi] are: x[0,π3)(5π3,2π]x \in \left[ 0, \frac{\pi}{3} \right) \cup \left( \frac{5\pi}{3}, 2\pi \right]

Would you like more details or have any questions?

Here are some related questions:

  1. How do you solve the inequality sin(x)>12\sin(x) > \frac{1}{2} over the interval [0,2π][0, 2\pi]?
  2. What is the general solution to the equation cos(x)=12\cos(x) = \frac{1}{2}?
  3. How do you find the maximum and minimum values of the function f(x)=2cos(x)1f(x) = 2 \cos(x) - 1?
  4. What is the graphical interpretation of cos(x)>12\cos(x) > \frac{1}{2}?
  5. How do the solutions of cos(x)=12\cos(x) = \frac{1}{2} change if the interval is [0,4π][0, 4\pi]?

Tip: When solving trigonometric inequalities, it's useful to first determine the critical points where the inequality changes sign and then consider the behavior within each interval defined by these points.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Inequalities
Cosine Function

Formulas

\(2 \cos(x) - 1 > 0\)
\(\cos(x) > \frac{1}{2}\)

Theorems

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Suitable Grade Level

High School