Calculate the average rate of change between two points on a function.
Formula: [f(x₂) – f(x₁)] / (x₂ – x₁)
Result:
Calculate the derivative (instantaneous rate) for a polynomial term axⁿ.
Function: f(x) = axⁿ | Derivative: f'(x) = anxⁿ⁻¹
Result:
Understanding Rate of Change in Calculus
In calculus, the Rate of Change describes how one quantity changes in relation to another. This is most commonly represented as the slope of a line on a graph.
1. Average Rate of Change
This is the slope of the secant line passing through two points (x₁, y₁) and (x₂, y₂). It represents the total change divided by the total time or interval. If you are driving, your average speed for the whole trip is the average rate of change of your position.
2. Instantaneous Rate of Change
This is the core of differential calculus. It is the slope of the tangent line at a specific point. It is calculated by taking the derivative of the function. For a power function like f(x) = axⁿ, the rate of change at any point is f'(x) = n * ax^(n-1).
Practical Example
Imagine an object's position is defined by f(t) = 5t².
Average Rate (t=1 to t=3): At t=1, f(1)=5. At t=3, f(3)=45. Average rate = (45 – 5) / (3 – 1) = 40 / 2 = 20 units/sec.
Instantaneous Rate (at t=2): The derivative is f'(t) = 10t. At t=2, the rate is 10(2) = 20 units/sec.
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var deltaY = fx2 – fx1;
var deltaX = x2 – x1;
var rate = deltaY / deltaX;
resultDisplay.innerHTML = rate.toFixed(4);
explanation.innerHTML = "The slope of the secant line is (" + fx2 + " – " + fx1 + ") / (" + x2 + " – " + x1 + ") = " + deltaY + " / " + deltaX;
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// Derivative of ax^n is (a*n)x^(n-1)
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var rate = newCoeff * Math.pow(x, newExp);
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explanation.innerHTML = "The derivative is f'(x) = " + newCoeff + "x^" + newExp + ". Evaluating at x=" + x + " gives " + newCoeff + "(" + x + ")^" + newExp + " = " + rate.toFixed(4);
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