Math Problem Statement

Suppose you want to find the area of the region R between the graphs of f(x) and g(x) on the interval [a, b], as illustrated in the figure. Which integral(s) should you evaluate to find the total area of R?

Solution

The question asks which integral(s) to evaluate in order to find the total area of the region RR between the graphs of f(x)f(x) and g(x)g(x) on the interval [a,b][a, b]. In the diagram, the region RR is shaded, and the curves cross each other at points bb, cc, and dd, indicating that the difference between the functions changes sign at these points.

To calculate the total area between two curves, we need to integrate the absolute difference between the functions. This is done by determining which function is greater over each sub-interval:

  1. From aa to bb, the function g(x)g(x) is above f(x)f(x), so we integrate g(x)f(x)g(x) - f(x).
  2. From bb to cc, f(x)f(x) is above g(x)g(x), so we integrate f(x)g(x)f(x) - g(x).
  3. From cc to dd, g(x)g(x) is again above f(x)f(x), so we integrate g(x)f(x)g(x) - f(x).
  4. Finally, from dd to ee, f(x)f(x) is above g(x)g(x), so we integrate f(x)g(x)f(x) - g(x).

The correct expression for the total area is:

A=ab(g(x)f(x))dx+bc(f(x)g(x))dx+cd(g(x)f(x))dx+de(f(x)g(x))dxA = \int_a^b (g(x) - f(x)) \, dx + \int_b^c (f(x) - g(x)) \, dx + \int_c^d (g(x) - f(x)) \, dx + \int_d^e (f(x) - g(x)) \, dx

This matches option 4 in the list of choices.

Would you like any further clarification on this? Here are some related questions you could explore:

  1. How do you determine which function is on top for integration?
  2. Why is the absolute value important when finding areas between curves?
  3. How would you approach this problem if you were not given points b,c,db, c, d?
  4. Can this method be extended to three-dimensional regions?
  5. What happens if the curves overlap in more than one region?

Tip: When calculating the area between curves, always pay attention to where the curves intersect, as this changes which function is the upper or lower curve.

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Math Problem Analysis

Mathematical Concepts

Definite Integrals
Area Between Curves
Calculus

Formulas

A = \int_a^b (g(x) - f(x)) \, dx + \int_b^c (f(x) - g(x)) \, dx + \int_c^d (g(x) - f(x)) \, dx + \int_d^e (f(x) - g(x)) \, dx

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12, College-level Calculus