Interactive: Definite Integral

Definite Integral: If \(f\) is a continuous function defined on the interval \([a, b]\) that is divided into \(n\) equal subintervals \(\Delta x = \frac{{b - a}}{n}\) where \(x_i^*\) lies in the ith subinterval then the definite integral of \(f\) from \(a\) to \(b\) follows:

\[\int_a^b {f\left( x \right)dx} = \mathop {\lim }\limits_{n \to \infty } \sum\limits_{i = 1}^n {f\left( {x_i^*} \right)} \,\Delta x\]

Instructions: Drag the slider to see that the area under the curve is the limit of Riemann sums. You can also change the sums to left, middle, right, and trapezoidal below the graph.

Riemann Sum: Left Middle Right Trapezoidal

Interactive: Derivative of a Function

Derivative of a Function at \(a\), if it exists:

\[f'\left( a \right) = \mathop {\lim }\limits_{h \to 0} \frac{{f\left( {a + h} \right) - f\left( a \right)}}{h}\]

Instructions: Drag the green dot representing a+h toward a to simulate h tending toward zero.

Interactive: Tangent Line at a Point

Definition: The tangent line to the curve \(y = f(x)\) at the point \(P(a, f(a))\) is the line through \(P\) with slope

\[m = \mathop {\lim }\limits_{x \to a} \frac{{f\left( x \right) - f\left( a \right)}}{{x - a}}\]

provided that this limit exists.

Instructions: With the mouse, move the x-value toward a to see that the tangent line is the limiting position of the secant line shown dashed. You can also move the points on the function. Refresh browser to start over.