Antiderivatives: Fresh Take

  • Understand indefinite integrals and learn how to find basic antiderivatives for functions
  • Use the rule for integrating functions raised to a power
  • Use antidifferentiation to solve simple initial-value problems

Finding the Antiderivative

The Main Idea 

  • Antidifferentiation is the reverse process of differentiation
  • A function [latex]F(x)[/latex] is an antiderivative of [latex]f(x)[/latex] if [latex]F'(x) = f(x)[/latex] for all [latex]x[/latex] in the domain of [latex]f[/latex]
  • General Form of Antiderivatives:
    • If [latex]F(x)[/latex] is an antiderivative of [latex]f(x)[/latex], then [latex]F(x) + C[/latex] is the general form of all antiderivatives of [latex]f(x)[/latex], where [latex]C[/latex] is any constant

Find all antiderivatives of [latex]f(x)= \sin x[/latex].

Find the general antiderivative of [latex]f(x) = x\sin(x) + x^2\cos(x)[/latex].

Indefinite Integrals

The Main Idea 

  • Definition of Indefinite Integral:
    • Notation: [latex]\int f(x) dx = F(x) + C[/latex]
    • [latex]F(x)[/latex] is an antiderivative of [latex]f(x)[/latex]
    • [latex]C[/latex] is the constant of integration
  • Terminology:
    • [latex]\int[/latex] is the integral sign
    • [latex]f(x)[/latex] is the integrand
    • [latex]x[/latex] is the variable of integration
  • Key Properties:
    • Sum/Difference Rule: [latex]\int (f(x) \pm g(x)) dx = \int f(x) dx \pm \int g(x) dx[/latex]
    • Constant Multiple Rule: [latex]\int kf(x) dx = k\int f(x) dx[/latex]
  • Power Rule for Integrals:
    • [latex]\int x^n dx = \frac{x^{n+1}}{n+1} + C[/latex], for [latex]n \neq -1[/latex]
  • Common Indefinite Integrals:
    • [latex]\int \frac{1}{x} dx = \ln|x| + C[/latex]
    • [latex]\int e^x dx = e^x + C[/latex]
    • [latex]\int \sin x dx = -\cos x + C[/latex]
    • [latex]\int \cos x dx = \sin x + C[/latex]
    • [latex]\int \sec^2 x dx = \tan x + C[/latex]

Verify that [latex]\displaystyle\int x \cos x dx=x \sin x+ \cos x+C[/latex].

Evaluate [latex]\displaystyle\int (4x^3-5x^2+x-7) dx[/latex]

Evaluate the indefinite integral: [latex]\int (3x^4 - 2\sin x + 5e^x + \frac{4}{x}) dx[/latex]

Initial-Value Problems

The Main Idea 

  • Definition of Differential Equation:
    • An equation relating an unknown function and one or more of its derivatives
  • Initial-Value Problem:
    • A differential equation with an additional condition
    • Condition typically specifies the function value at a particular point
    • Example:
      • [latex]\frac{dy}{dx} = f(x), y(x_0) = y_0[/latex]
  • Solving Initial-Value Problems:
    • Find the general solution of the differential equation
    • Use the initial condition to determine the specific solution
  • Applications:
    • Motion problems (position, velocity, acceleration)
    • Growth and decay models
    • Numerous real-world scenarios in physics, engineering, and other fields

Suppose the car is traveling at the rate of [latex]44[/latex] ft/sec. How long does it take for the car to stop? How far will the car travel?