plotXpose is a companion app with the book Mathematics for Electrical Engineering and Computing by Mary Attenborough - click for more info
 

Integral

To switch the display of the integral on or off then select the Integral check box on the “View” window. This window appears by selecting the View command.

Two methods are available for calculating the integral either: Simpson’s rule cannot be used if there is irregular sampling. The integral will not be calculated, by either method, if there are Undefined Values of the function.

You are also asked to specify the initial value for t. This is the value used as the lower limit of the integration. The integral at any point represents the area under the graph calculated from the initial value for t. At the initial value the integral will equal 0.

The integral is calculated at the current Sampling Interval and displayed over the currently defined Settings. Sample points are joined by straight line segments, where possible, to give the appearance of a continuous function.

plotXpose can be used to calculate the mean or r.m.s. value of a function y(t).

To calculate the mean value of y(t)

Plot the graph of y/(b-a) with a t-axis range which includes the interval [a,b]. Now set the integral to calculate from t=a. Use the Display Position to read the value of the integral at t=b.

To calculate the r.m.s. value of y(t)

Plot the graph of y^2/(b-a) with a t-axis range which includes the interval [a,b]. Now set the integral to calculate from t=a. Use the Display Position to read the value of the integral at t=b and then take the square root of the result using a calculator.