Use three rectangles to approximate the area under the curve of from to using the midpoint rule.
Table of contents
- 0. Functions7h 52m
- Introduction to Functions16m
- Piecewise Functions10m
- Properties of Functions9m
- Common Functions1h 8m
- Transformations5m
- Combining Functions27m
- Exponent rules32m
- Exponential Functions28m
- Logarithmic Functions24m
- Properties of Logarithms34m
- Exponential & Logarithmic Equations35m
- Introduction to Trigonometric Functions38m
- Graphs of Trigonometric Functions44m
- Trigonometric Identities47m
- Inverse Trigonometric Functions48m
- 1. Limits and Continuity2h 2m
- 2. Intro to Derivatives1h 33m
- 3. Techniques of Differentiation3h 18m
- 4. Applications of Derivatives2h 38m
- 5. Graphical Applications of Derivatives6h 2m
- 6. Derivatives of Inverse, Exponential, & Logarithmic Functions2h 37m
- 7. Antiderivatives & Indefinite Integrals1h 26m
- 8. Definite Integrals4h 44m
- 9. Graphical Applications of Integrals2h 27m
- 10. Physics Applications of Integrals 3h 16m
- 11. Integrals of Inverse, Exponential, & Logarithmic Functions2h 34m
- 12. Techniques of Integration7h 39m
- 13. Intro to Differential Equations2h 55m
- 14. Sequences & Series5h 36m
- 15. Power Series2h 19m
- 16. Parametric Equations & Polar Coordinates7h 58m
8. Definite Integrals
Estimating Area with Finite Sums
Problem 5.R.1d
Textbook Question
Explain why or why not Determine whether the following statements are true and give an explanation or counterexample. Assume ƒ and ƒ' are continuous functions for all real numbers.
(d) If ƒ is continuous on [a,b] and ∫ₐᵇ |ƒ(𝓍)| d𝓍 = 0 , then ƒ(𝓍) = 0 on [a,b] .

1
Step 1: Begin by understanding the integral ∫ₐᵇ |ƒ(𝓍)| d𝓍 = 0. This represents the area under the curve of the absolute value of ƒ(𝓍) over the interval [a, b]. If this integral equals zero, it implies that the absolute value of ƒ(𝓍) contributes no area over the interval.
Step 2: Recall that the absolute value function |ƒ(𝓍)| is always non-negative. Therefore, for the integral of |ƒ(𝓍)| to equal zero, the function |ƒ(𝓍)| must be zero everywhere on [a, b].
Step 3: If |ƒ(𝓍)| = 0 for all 𝓍 in [a, b], then ƒ(𝓍) must also equal 0 for all 𝓍 in [a, b]. This is because the absolute value of a number is zero only when the number itself is zero.
Step 4: Conclude that the statement is true. If ƒ is continuous on [a, b] and ∫ₐᵇ |ƒ(𝓍)| d𝓍 = 0, then ƒ(𝓍) = 0 on [a, b]. The reasoning is based on the properties of the absolute value function and the definition of the integral.
Step 5: If needed, provide a counterexample to test the logic. For instance, consider a function ƒ(𝓍) that is non-zero at any point in [a, b]. The integral ∫ₐᵇ |ƒ(𝓍)| d𝓍 would not be zero, confirming the validity of the statement.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Continuity of Functions
A function is continuous on an interval if there are no breaks, jumps, or holes in its graph. This means that for every point in the interval, the function approaches the same value from both sides. Continuity is crucial for applying the Fundamental Theorem of Calculus, which connects differentiation and integration.
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Intro to Continuity
Definite Integral and Absolute Value
The definite integral of a function over an interval gives the net area under the curve of that function. When considering the integral of the absolute value of a function, ∫ₐᵇ |ƒ(𝓍)| d𝓍 = 0 implies that the function must be zero almost everywhere on that interval, as the absolute value cannot be negative, and the only way for the integral to equal zero is if the function itself is zero.
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Definition of the Definite Integral
Properties of Integrals
Integrals have specific properties that help in understanding the behavior of functions. One important property is that if the integral of a non-negative function over an interval is zero, then the function must be zero at every point in that interval. This property is essential for analyzing the statement in the question regarding the function ƒ and its integral.
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Properties of Functions
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