Math Problem Statement

Solve the inequality to two decimal places where 0 ≤ 𝑥 ≤ 2𝜋, 4 cos(𝑥) + 2 > 𝜋

Solution

We are given the inequality:

4cos(x)+2>π4 \cos(x) + 2 > \pi and the interval for xx is 0x2π0 \leq x \leq 2\pi.

Step 1: Simplify the inequality

First, subtract 2 from both sides of the inequality:

4cos(x)>π24 \cos(x) > \pi - 2

Now compute π2\pi - 2:

π23.142=1.14\pi - 2 \approx 3.14 - 2 = 1.14

So the inequality becomes:

4cos(x)>1.144 \cos(x) > 1.14

Step 2: Solve for cos(x)\cos(x)

Now divide both sides of the inequality by 4:

cos(x)>1.144\cos(x) > \frac{1.14}{4}

cos(x)>0.285\cos(x) > 0.285

Step 3: Determine the range of xx

We need to find the values of xx in the interval 0x2π0 \leq x \leq 2\pi such that cos(x)>0.285\cos(x) > 0.285.

The cosine function is positive in the first and fourth quadrants, so we will find the reference angle where cos(x)=0.285\cos(x) = 0.285.

Using the inverse cosine function:

x=cos1(0.285)1.28 radiansx = \cos^{-1}(0.285) \approx 1.28 \text{ radians}

Thus, in the first quadrant, x=1.28x = 1.28.

In the fourth quadrant, the corresponding solution is:

x=2π1.286.281.28=5.00 radiansx = 2\pi - 1.28 \approx 6.28 - 1.28 = 5.00 \text{ radians}

Step 4: Solution intervals

Since cos(x)\cos(x) is greater than 0.285 between these values, the solution for xx is:

[ x \in [0, 1.28] \cup [5.00, 2\pi] ]

In decimal form:

[ x \in [0, 1.28] \cup [5.00, 6.28] ]

Thus, the values of xx that satisfy the inequality 4cos(x)+2>π4 \cos(x) + 2 > \pi are in the intervals [0,1.28][5.00,6.28][0, 1.28] \cup [5.00, 6.28].

Do you have any further questions or want more details?

Here are 5 related questions to expand on this topic:

  1. How do you find the cosine of an angle in different quadrants?
  2. What are the properties of the cosine function over the interval [0,2π][0, 2\pi]?
  3. Can you explain the significance of the inverse trigonometric functions?
  4. How does the cosine graph look in the range [0,2π][0, 2\pi]?
  5. How would the solution change if the inequality was 4cos(x)+2<π4 \cos(x) + 2 < \pi?

Tip: Always ensure your calculator is in the correct mode (radians or degrees) based on the given problem context.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Inequalities
Inverse Trigonometric Functions

Formulas

4 cos(x) + 2 > π
cos(x) = adjacent / hypotenuse
x = cos^(-1)(value)

Theorems

Cosine Function Properties
Range of the Cosine Function in the Interval [0, 2π]

Suitable Grade Level

Grades 11-12