Math Problem Statement

Write the integral as a sum of integrals without absolute values and evaluate: \( \int_{\pi/6}^{\pi/2} |\cos x| \, dx \)

Solution

The integral provided is

π/6π/2cosxdx\int_{\pi/6}^{\pi/2} |\cos x| \, dx

To evaluate it without the absolute value, we analyze the behavior of cosx\cos x over the interval [π/6,π/2][\pi/6, \pi/2]. In this range, cosx0\cos x \geq 0, so the absolute value of cosx\cos x simplifies to cosx\cos x itself.

Now, the integral becomes:

π/6π/2cosxdx\int_{\pi/6}^{\pi/2} \cos x \, dx

The antiderivative of cosx\cos x is sinx\sin x, so:

π/6π/2cosxdx=sinxπ/6π/2\int_{\pi/6}^{\pi/2} \cos x \, dx = \sin x \bigg|_{\pi/6}^{\pi/2}

Substituting the bounds:

sin(π/2)sin(π/6)\sin(\pi/2) - \sin(\pi/6)

We calculate:

sin(π/2)=1andsin(π/6)=12\sin(\pi/2) = 1 \quad \text{and} \quad \sin(\pi/6) = \frac{1}{2}

Thus:

112=121 - \frac{1}{2} = \frac{1}{2}

The value of the integral is:

12\boxed{\frac{1}{2}}

Would you like me to explain the steps further or provide additional examples?

Related Questions:

  1. How do absolute values affect the integral of a function in general?
  2. What if the interval had included a region where cosx<0\cos x < 0? How would that change the solution?
  3. Can we generalize this result to any interval where the sign of cosx\cos x is constant?
  4. How does the Fundamental Theorem of Calculus relate to solving this problem?
  5. Could this integral be solved numerically for more complex cases?

Tip:

Always check the behavior of the function under the absolute value to determine whether splitting the integral is necessary.

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Math Problem Analysis

Mathematical Concepts

Integration
Absolute Value
Trigonometric Functions

Formulas

\( \int \cos x \, dx = \sin x + C \)

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12