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Fundamental theorem of calculus and accumulation functions

Fundamental theorem of calculus and accumulation functions

The Fundamental Theorem of Calculus connects differentiation and integration, providing a powerful framework for understanding these two core concepts in calculus.

  1. Part 1 states that if ff is a continuous function on the interval [a,b][a, b], then the function defined by the accumulation function F(x)=axf(t)dtF(x) = \int_a^x f(t) \, dt for x[a,b]x \in [a, b] is continuous, differentiable, and F(x)=f(x)F'(x) = f(x). This means that the derivative of the accumulation function at any point gives the value of the original function at that point.

  2. Part 2 states that if FF is an antiderivative of ff on [a,b][a, b], then the definite integral of ff from aa to bb can be evaluated as abf(x)dx=F(b)F(a)\int_a^b f(x) \, dx = F(b) - F(a). This establishes a direct relationship between the area under the curve of a function and its antiderivatives.

Overall, these concepts illustrate how integration can effectively "accumulate" values derived from a function, and they establish a foundational link between these two central operations in calculus.

Part 1: The fundamental theorem of calculus and accumulation functions

The fundamental theorem of calculus shows how, in some sense, integration is the opposite of differentiation.

Certainly! Here are the key points to focus on when studying "The Fundamental Theorem of Calculus and Accumulation Functions":

  1. Fundamental Theorem of Calculus (FTC):

    • Part 1: States that if ff is continuous on [a,b][a, b] and FF is an antiderivative of ff on [a,b][a, b], then:
      abf(x)dx=F(b)F(a)\int_a^b f(x) \, dx = F(b) - F(a)
    • Part 2: If ff is continuous on an interval [a,b][a, b], then the function defined by:
      F(x)=axf(t)dtF(x) = \int_a^x f(t) \, dt
      for xx in [a,b][a, b] is continuous on [a,b][a, b], differentiable on (a,b)(a, b), and F(x)=f(x)F'(x) = f(x).
  2. Accumulation Functions:

    • An accumulation function, represented as F(x)F(x), measures the total accumulation of the quantity represented by f(t)f(t) from aa to xx.
    • Recognizing how the derivative of the accumulation function relates back to the original function f(x)f(x) is crucial.
  3. Connection between Integration and Differentiation:

    • Understand how the FTC bridges the concepts of integration (finding areas) and differentiation (finding rates of change).
    • Be able to identify different contexts and applications where this relationship is utilized.
  4. Practical Applications:

    • Know how to apply the FTC to solve real-world problems, including finding total quantities from rates of change.
    • Be familiar with interpreting the physical meaning represented by the functions involved, including accumulation.
  5. Graphical Interpretation:

    • Visualizing the area under curves and how it relates to the values of accumulation functions and their derivatives can enhance understanding.
  6. Properties of Definite Integrals:

    • Review properties of definite integrals (e.g., linearity, interval addition, and the effect of changing limits) and how they fit within the FTC framework.

Studying these key points will provide a solid foundation on the Fundamental Theorem of Calculus and accumulation functions.

Part 2: Functions defined by definite integrals (accumulation functions)

Understanding that a function can be defined using a definite integral. Thinking about how to evaluate functions defined this way.

Certainly! Here are the key points for studying functions defined by definite integrals (accumulation functions):

  1. Definition of Accumulation Function:

    • An accumulation function F(x)F(x) defined by a definite integral: F(x)=axf(t)dtF(x) = \int_{a}^{x} f(t) \, dt, where f(t)f(t) is the integrand and aa is a constant.
  2. Interpretation:

    • F(x)F(x) represents the area under the curve f(t)f(t) from t=at = a to t=xt = x.
  3. Fundamental Theorem of Calculus:

    • If ff is continuous on [a,b][a, b]:
      • F(x)=f(x)F'(x) = f(x) (the derivative of the accumulation function is the integrand).
  4. Properties of Accumulation Functions:

    • F(a)=0F(a) = 0 since there is no area under the curve from aa to aa.
    • If x1<x2x_1 < x_2, then F(x2)F(x1)=x1x2f(t)dtF(x_2) - F(x_1) = \int_{x_1}^{x_2} f(t) \, dt (the net area between x1x_1 and x2x_2).
  5. Continuity:

    • Accumulation functions F(x)F(x) are continuous wherever f(t)f(t) is continuous.
  6. Increasing/Decreasing Behavior:

    • If f(t)>0f(t) > 0 on an interval, F(x)F(x) is increasing.
    • If f(t)<0f(t) < 0 on an interval, F(x)F(x) is decreasing.
  7. Second Fundamental Theorem of Calculus:

    • For a continuous function ff, the accumulation function can be differentiated to recover the original function.
  8. Applications:

    • Used in determining total accumulated quantities, such as distance from velocity functions, or total area from density functions.

These points form the foundation for understanding how functions defined by definite integrals work and how they relate to calculus concepts.

Part 3: Finding derivative with fundamental theorem of calculus

The Fundamental Theorem of Calculus tells us that the derivative of the definite integral from 𝘢 to 𝘹 of ƒ(𝑡)𝘥𝑡 is ƒ(𝘹), provided that ƒ is continuous. See how this can be used to evaluate the derivative of accumulation functions.

Here are the key points to learn when studying the application of the Fundamental Theorem of Calculus (FTC) for finding derivatives:

  1. Understanding the Fundamental Theorem of Calculus:

    • The FTC consists of two parts:
      • Part 1 states that if ff is continuous on [a,b][a, b] and FF is an antiderivative of ff on [a,b][a, b], then:
        abf(x)dx=F(b)F(a)\int_a^b f(x) \, dx = F(b) - F(a)
      • Part 2 states that if ff is continuous on an interval and F(x)=axf(t)dtF(x) = \int_a^x f(t) \, dt, then F(x)=f(x)F' (x) = f(x).
  2. Finding Derivatives Using the FTC:

    • When you need to differentiate an integral function F(x)=axf(t)dtF(x) = \int_a^x f(t) \, dt, apply Part 2 of the FTC directly:
      F(x)=f(x)F'(x) = f(x)
  3. Application of the Chain Rule:

    • For composite functions where the upper limit is not just xx (e.g., F(g(x))=ag(x)f(t)dtF(g(x)) = \int_a^{g(x)} f(t) \, dt), use the chain rule:
      ddxF(g(x))=f(g(x))g(x)\frac{d}{dx} F(g(x)) = f(g(x)) \cdot g'(x)
  4. Continuity Requirement:

    • Ensure that the function f(x)f(x) is continuous on the interval used for the integration when applying the FTC.
  5. Practice with Examples:

    • Solve various problems that involve both finding derivatives of definite integrals and using the theorem to establish connections between integration and differentiation.

By mastering these points, you'll effectively use the Fundamental Theorem of Calculus to find derivatives.

Part 4: Finding derivative with fundamental theorem of calculus: chain rule

The Fundamental Theorem of Calculus tells us how to find the derivative of the integral from 𝘢 to 𝘹 of a certain function. But what if instead of 𝘹 we have a function of 𝘹, for example sin(𝘹)? Then we need to also use the chain rule.

Here are the key points to learn when studying "Finding derivatives with the Fundamental Theorem of Calculus (FTC) and the Chain Rule":

  1. Fundamental Theorem of Calculus:

    • Establishes the relationship between differentiation and integration.
    • Part 1 states that if F(x)=axf(t)dtF(x) = \int_{a}^{x} f(t) \, dt, then F(x)=f(x)F'(x) = f(x).
    • Part 2 states that if FF is an antiderivative of ff, then abf(x)dx=F(b)F(a)\int_{a}^{b} f(x) \, dx = F(b) - F(a).
  2. Chain Rule:

    • Used to differentiate composite functions.
    • If y=g(u)y = g(u) and u=f(x)u = f(x), then dydx=dydududx\frac{dy}{dx} = \frac{dy}{du} \cdot \frac{du}{dx}.
  3. Applying Chain Rule with FTC:

    • When differentiating an integral with a variable limit, apply the Chain Rule alongside the FTC.
    • For y=g(x)h(x)f(t)dty = \int_{g(x)}^{h(x)} f(t) \, dt, differentiate as follows:
      dydx=f(h(x))h(x)f(g(x))g(x)\frac{dy}{dx} = f(h(x)) \cdot h'(x) - f(g(x)) \cdot g'(x)
    • This accounts for both upper and lower limits being functions of xx.
  4. Example Practice:

    • Work through examples involving both the FTC and Chain Rule to solidify understanding.
    • Practice finds derivatives of functions defined by integrals where limits are functions of xx.
  5. Common Pitfalls:

    • Remember that when applying the Chain Rule, you must differentiate both the limits and the integrand appropriately.
    • Misapplying limits or forgetting to include the derivative of the limits can lead to incorrect results.

By mastering these concepts, you'll have a solid foundation for finding derivatives using the FTC in conjunction with the Chain Rule.