The waveform generator is implemented in JavaScript and the sampled values of your waveform are passed to the Java applet, which plots the signal, performs the FFT calculations, and plots the frequency spectrum. Note, however, that while JavaScript offers more flexibility, it doesn't run as fast as Java. A larger number of samples gives a finer spectral resolution, but it will take longer to generate the sampled values, particularly since the waveform calculations are done in JavaScript. Keep in mind the constraints imposed by the sampling theorem. Type in the expression representing the required waveform.
Further examples showing how to construct suitable expressions are available.
Click the Plot signal button to generate the sampled values of the signal and plot the signal waveform as a function of time. The plot is automatically scaled to the maximum value. Click the Plot spectrum button to compute display the magnitude frequency spectrum of the signal. The plot is scaled to the largest component of the spectrum. Note that you must first generate and plot the signal by pressing the Plot signal button before the frequency spectrum can be determined.