Integration - Definite Integrals

Definite Integrals

Fundamental Properties and Applications

A definite integral computes the **net area under a curve** between two specific limits. It is central to many areas of mathematics, science, and engineering.

  • \[ \int_a^b f(x) \, dx = F(x) \Big|_a^b = F(b) - F(a), \quad F'(x) = f(x). \]
  • \[ \int_a^b \{ f(x) \pm g(x) \} \, dx = \int_a^b f(x) \, dx \pm \int_a^b g(x) \, dx \]
  • \[ \int_a^b C f(x) \, dx = C \int_a^b f(x) \, dx \]
  • \[ \int_a^a f(x) \, dx = 0 \]
  • \[ \int_a^b f(x) \, dx = - \int_b^a f(x) \, dx \]
  • \[ \int_a^b f(x) \, dx = \int_a^c f(x) \, dx + \int_c^b f(x) \, dx \]
  • \[ \int_a^b f(x) \, dx = (b - a) f(c), \quad a \leq c \leq b \]
  • \[ \int_a^b f(x) g(x) \, dx = f(c) \int_a^b g(x) \, dx, \quad a \leq c \leq b, \quad g(x) \geq 0. \]

Terminology

  • Definite Integral: Represents the signed area under a curve from \( a \) to \( b \).
  • Limits of Integration: The lower and upper bounds \( a \) and \( b \).
  • Net Area: Area above the x-axis is positive; below is negative.
  • Mean Value Theorem for Integrals: There exists \( c \in [a, b] \) such that \( \int_a^b f(x) dx = (b - a)f(c) \).

Applications

  • Calculating area between curves and axes.
  • Determining displacement and distance in physics.
  • Evaluating probability from continuous probability distributions.
  • Finding averages and expected values in statistics.
  • Used in economics for calculating total cost or revenue over time.
×

×