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Fundamental theorem of calculus and definite integrals

Fundamental theorem of calculus and definite integrals

The Fundamental Theorem of Calculus links the concepts of differentiation and integration, showing that they are essentially inverse processes. It consists of two main parts:

  1. First Part: If ff is continuous on an interval [a,b][a, b], then the function FF defined by the integral

    F(x)=axf(t)dtF(x) = \int_a^x f(t) \, dt

    for xx in [a,b][a, b] is continuous on that interval, differentiable on (a,b)(a, b), and F(x)=f(x)F'(x) = f(x).

  2. Second Part: It provides a method to evaluate definite integrals. It states that if 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).

Together, these principles allow us to calculate the area under a curve and relate it to the concept of accumulation and instantaneous rates of change.

Part 1: The fundamental theorem of calculus and definite integrals

There are really two versions of the fundamental theorem of calculus, and we go through the connection here.

Sure! Here are the key points to learn when studying "The Fundamental Theorem of Calculus and Definite Integrals":

  1. Fundamental Theorem of Calculus (FTC):

    • Part 1: If ff is continuous on [a,b][a, b], then the function FF defined by F(x)=axf(t)dtF(x) = \int_a^x f(t) \, dt is continuous on [a,b][a, b], differentiable on (a,b)(a, b), and F(x)=f(x)F'(x) = f(x).
    • Part 2: If FF is any 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)
  2. Definite Integrals:

    • Represents the signed area under the curve f(x)f(x) from aa to bb.
    • Denoted as abf(x)dx\int_a^b f(x) \, dx.
    • Can be computed using the antiderivative FF as described by Part 2 of the FTC.
  3. Properties of Definite Integrals:

    • Linearity: ab[cf(x)+g(x)]dx=cabf(x)dx+abg(x)dx\int_a^b [c \cdot f(x) + g(x)] \, dx = c \int_a^b f(x) \, dx + \int_a^b g(x) \, dx
    • Additivity: abf(x)dx=acf(x)dx+cbf(x)dx\int_a^b f(x) \, dx = \int_a^c f(x) \, dx + \int_c^b f(x) \, dx for any cc in [a,b][a, b].
    • Reversal of Limits: abf(x)dx=baf(x)dx\int_a^b f(x) \, dx = -\int_b^a f(x) \, dx
  4. Applications of the Fundamental Theorem:

    • Used to calculate definite integrals efficiently.
    • Provides a connection between differentiation and integration.
  5. Interpretation:

    • Relates the accumulation of quantities to their rates of change.
    • Highlights the fundamental relationship between a function and its area under the curve.

These points encapsulate the foundational aspects needed to understand the Fundamental Theorem of Calculus and its application to definite integrals.

Part 2: Antiderivatives and indefinite integrals

What's the opposite of a derivative?  It's something called the "indefinite integral".

When studying "Antiderivatives and Indefinite Integrals," focus on the following key points:

  1. Definition: An antiderivative of a function f(x)f(x) is a function F(x)F(x) such that F(x)=f(x)F'(x) = f(x). An indefinite integral represents the set of all antiderivatives of a function.

  2. Notation: The indefinite integral of f(x)f(x) is written as f(x)dx=F(x)+C\int f(x) \, dx = F(x) + C, where CC is the constant of integration.

  3. Basic Rules:

    • Power Rule: xndx=xn+1n+1+C\int x^n \, dx = \frac{x^{n+1}}{n+1} + C for n1n \neq -1.
    • Constant Multiple Rule: kf(x)dx=kf(x)dx\int k f(x) \, dx = k \int f(x) \, dx.
    • Sum Rule: [f(x)+g(x)]dx=f(x)dx+g(x)dx\int [f(x) + g(x)] \, dx = \int f(x) \, dx + \int g(x) \, dx.
  4. Common Integrals: Know the basic integrals, such as:

    • exdx=ex+C\int e^x \, dx = e^x + C
    • sin(x)dx=cos(x)+C\int \sin(x) \, dx = -\cos(x) + C
    • cos(x)dx=sin(x)+C\int \cos(x) \, dx = \sin(x) + C
  5. Integration Techniques:

    • Substitution: Useful for integrals involving composite functions.
    • Integration by Parts: udv=uvvdu\int u \, dv = uv - \int v \, du.
  6. Applications: Understanding how antiderivatives are used to solve problems in physics and engineering, such as calculating areas under curves and velocities from acceleration.

  7. Fundamental Theorem of Calculus: Connects differentiation and integration; 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).

  8. Graphical Interpretation: Antiderivatives can be visualized as the area under a curve of the function f(x)f(x).

By mastering these concepts, you will gain a solid foundation in understanding antiderivatives and indefinite integrals.