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A chart is a statement. Solve the page to draw it. 2 examples.
The free name in a series is the horizontal axis. It does not become an unknown. A label may be quoted, and the quotes are removed. A quote has no escape, and a quote that is not a label stops the solve. Useful keys are xrange, yrange, color, thickness, transparency, xlabel, ylabel, charttitle, chartwidth, and chartheight. The square-wave example uses if, which is documented on If and case.
Sinc
One curve.
Square wave, twelve terms
The series uses only the odd harmonics. Near the jump the overshoot stays, which is the Gibbs phenomenon. Solve it to draw the chart.