Area Under Graph Calculator

Area Under the Curve Calculator

Calculate the definite integral of a function $f(x) = Ax^2 + Bx + C$ using the Trapezoidal Rule.

Calculation Result

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Understanding the Area Under a Graph

The area under a graph (or the definite integral) represents the cumulative total of a variable over an interval. In physics, this might represent displacement (area under a velocity-time graph) or work done (area under a force-displacement graph). In statistics, it represents probability density.

The Trapezoidal Rule Formula

This calculator uses the Trapezoidal Rule, a numerical integration method that approximates the region under the graph of a function as a series of trapezoids. The formula is:

Area ≈ (Δx / 2) * [f(x₀) + 2f(x₁) + 2f(x₂) + … + 2f(xₙ₋₁) + f(xₙ)]

Where:

  • Δx = (b – a) / n
  • a = Lower limit of integration
  • b = Upper limit of integration
  • n = Number of sub-intervals

Real-World Example

Imagine a vehicle accelerating where the velocity function is v(t) = 2t² + 3t. To find the total distance traveled between 0 and 4 seconds:

  1. Set Lower Limit (a) to 0.
  2. Set Upper Limit (b) to 4.
  3. Set Coefficient A to 2, B to 3, and C to 0.
  4. Increase Intervals (n) (e.g., 100) for higher precision.
  5. The result provides the total distance in units (e.g., meters).
function calculateArea() { var a = parseFloat(document.getElementById('lowerLimit').value); var b = parseFloat(document.getElementById('upperLimit').value); var n = parseInt(document.getElementById('intervals').value); var A = parseFloat(document.getElementById('coeffA').value); var B = parseFloat(document.getElementById('coeffB').value); var C = parseFloat(document.getElementById('coeffC').value); if (isNaN(a) || isNaN(b) || isNaN(n) || isNaN(A) || isNaN(B) || isNaN(C)) { alert("Please enter valid numerical values."); return; } if (n <= 0) { alert("Number of intervals must be greater than zero."); return; } // Function f(x) = Ax^2 + Bx + C function f(x) { return (A * x * x) + (B * x) + C; } var dx = (b – a) / n; var sum = f(a) + f(b); for (var i = 1; i 0 ? "+ " + B + "x " : (B 0 ? "+ " + C : (C < 0 ? C : "")); document.getElementById('formulaDetails').innerHTML = "Calculated using " + n + " intervals for " + equationText + " from x=" + a + " to x=" + b + "."; }

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