Glossary
Absolute Value
The non-negative value of a number or expression, used in area calculations to ensure all contributions are positive regardless of whether the curve is above or below the x-axis.
Example:
When calculating the total distance a particle travels, even if it moves backward, you take the absolute value of its displacement for each segment to sum them up.
Absolute Value
The non-negative magnitude of a real number, representing its distance from zero regardless of its sign.
Example:
If a definite integral yields , the actual area is the absolute value of , which is square units.
Absolute Value (Modulus)
The non-negative magnitude of a real number, representing its distance from zero regardless of its sign.
Example:
When calculating the actual physical area, you must take the absolute value of the definite integral, as area cannot be negative.
Accumulation of Change
The conceptual understanding that a definite integral sums up infinitesimal changes of a quantity over an interval to find the total change or net effect.
Example:
If a function represents the rate of water flowing into a tank, the accumulation of change over an hour tells you the total volume of water added.
Area Between Two Curves
The region enclosed by two functions over a specified interval, calculated using definite integrals.
Example:
To find the Area Between Two Curves like y=x² and y=x+2, you integrate the difference of the functions over their intersection points.
Area Between a Curve and the Y-Axis
The region bounded by a curve, the y-axis, and two horizontal lines (or y-intercepts), calculated using integration with respect to y.
Example:
Calculating the area between a curve and the y-axis for from to helps visualize the space enclosed.
Area Between a Curve and the x-Axis
The region bounded by a function's graph, the x-axis, and two vertical lines (limits of integration), calculated using definite integrals.
Example:
To determine the total ground covered by a projectile's parabolic path, you would calculate the area between a curve and the x-axis.
Areas Partly Above and Below the x-axis
A method for calculating the total area enclosed by a curve and the x-axis when parts of the curve are above and parts are below the x-axis, requiring separate integration for each segment and summing absolute values.
Example:
To find the total area of the region bounded by y = cos(x) and the x-axis from x=0 to 2π, you must use the areas partly above and below the x-axis method, integrating separately for positive and negative regions.
Bounds (Limits of Integration)
The upper and lower values of the independent variable that define the specific interval over which a definite integral is evaluated.
Example:
In ∫₀¹ (x²) dx, 0 and 1 are the Bounds or Limits of Integration.
Curve
A continuous line or outline, typically representing the graph of a function in a coordinate plane.
Example:
The path of a thrown ball can be modeled by a parabolic curve, and calculus helps find the area under it.
Curves
Graphical representations of functions, typically plotted on a coordinate plane, whose shapes are defined by their equations.
Example:
The parabola y=x² and the line y=x are examples of Curves whose enclosed area can be calculated.
Definite Integral
The integral of a function over a specified interval, representing the net area between the function and the x-axis.
Example:
To calculate the total displacement of a rocket from launch (t=0) to engine cutoff (t=10s) given its velocity function, you would compute the definite integral of the velocity over that time interval.
Definite Integral
An integral that computes the net accumulation of a quantity, such as the area under a curve or between curves, over a specific interval defined by upper and lower limits.
Example:
Calculating the Definite Integral of a velocity function from t=0 to t=5 gives the total displacement over that time.
Definite Integral
A mathematical operation that calculates the net signed area between a function's graph and the x-axis over a specified interval.
Example:
Using a definite integral from 0 to 5 for a velocity function gives the total displacement of an object over that time.
Definite Integral
An integral with specified upper and lower limits, used to calculate the net area under a curve or between curves over a given interval.
Example:
Using a definite integral like to find the exact area under the parabola from to .
Function Order (Above/Below Function)
The principle of identifying which function has greater y-values (or x-values for integration with respect to y) over a given interval, ensuring the integrand is non-negative.
Example:
When integrating with respect to x, always place the Function Order of the curve that is graphically above the other first in the integrand to ensure a positive area.
Function x = g(y)
A mathematical relationship where the independent variable is $y$ and the dependent variable is $x$, meaning $x$ is expressed in terms of $y$.
Example:
To find the area with respect to the y-axis, you must first rearrange into the form of a function x = g(y), which would be .
Integrand
The function that is being integrated within an integral expression.
Example:
In the integral ∫(x² + 3x) dx, the expression (x² + 3x) is the Integrand.
Integration Limits
The upper and lower bounds of a definite integral, which define the specific interval over which the integration is performed.
Example:
When finding the area between and the y-axis from to , and are the integration limits.
Integration with respect to x
The process of finding the area between curves by setting up the integral in terms of the variable x, typically when functions are given as y = f(x).
Example:
To find the area between y=x² and y=x+2, you would use Integration with respect to x, setting up the integral as ∫(x+2 - x²) dx.
Integration with respect to y
The process of finding the area between curves by setting up the integral in terms of the variable y, typically when functions are given as x = f(y).
Example:
If you have curves like x=y² and x=y+2, you would use Integration with respect to y, setting up the integral as ∫(y+2 - y²) dy.
Intersection Points
Points where two curves meet or cross each other, which are critical for determining the limits of integration when calculating areas between curves.
Example:
To find the area enclosed by the parabola y = x^2 and the line y = x + 2, you first identify their intersection points to define the boundaries of integration.
Intersection Points
The specific coordinates where two or more curves meet or cross each other, often serving as the limits of integration when finding the area between them.
Example:
Finding the Intersection Points of y=x² and y=4 is the first step to determine the bounds for calculating the area enclosed by them.
Interval
A continuous range of values for a variable, often denoted by [a, b], over which a function is considered or an integral is evaluated.
Example:
When finding the area between two curves from x=0 to x=2, the Interval is [0, 2].
Limits (of integration)
The upper and lower bounds of an interval over which a definite integral is calculated, defining the specific region of interest.
Example:
When finding the area under from to , 1 and 3 are the limits of integration.
Logarithms
The inverse operation to exponentiation, used to find the power to which a base number must be raised to produce a given number.
Example:
When solving for x in 2^x = 8, you use Logarithms to find that x = log₂(8) = 3.
Multiple Integrals
In this context, it refers to the strategy of splitting a complex area calculation into several definite integrals, often due to changes in which function is 'on top' or where the curve crosses the x-axis.
Example:
When finding the area of a region bounded by three different functions, you might need to use multiple integrals, each with different limits and integrand functions, to cover the entire region.
Negative Area Integrals
A definite integral whose value is negative, indicating that the area lies predominantly to the left of the y-axis (or below the x-axis for $\int f(x) dx$).
Example:
If you integrate from to , the result will be a negative area integral because the curve is to the left of the y-axis in that interval.
Negative Areas
A result of a definite integral when the function's graph lies below the x-axis over the interval, indicating a signed area rather than a physical area.
Example:
If a definite integral for a profit function yields a negative area, it signifies a net loss over that period.
Top Function
In the context of finding the area between two curves, the function with the higher y-value (or further to the right for integration with respect to y) within a specified interval.
Example:
When finding the area between y = √x and y = x^2 from x=0 to x=1, y = √x is the top function because its values are greater than or equal to y = x^2 in that interval.
Total Areas Between Two Curves
A method for calculating the total area enclosed by two intersecting curves, typically involving integrating the difference between the 'top' and 'bottom' functions over relevant intervals.
Example:
Determining the land area shared by two overlapping circular fields would involve calculating the total areas between two curves representing the field boundaries.
Y-Axis Intercepts
The points where a graph crosses or touches the y-axis, occurring when the x-coordinate is zero.
Example:
For the curve , the y-axis intercepts are found by setting , yielding .
x-axis intercepts
The points where a function's graph crosses or touches the x-axis, meaning the y-coordinate is zero.
Example:
Finding the x-axis intercepts of a quadratic function helps determine the starting and ending points for calculating the area it encloses with the x-axis.