File:Synthesis square.gif

' The frames of the animation can be drawn
' by the code below in BASIC. The animation
' is made by collecting the frames in an
' image editor such as GIMP.

REM Constant
pi=4*atn(1)
REM Set up plotting area
screen 12
window (0,-2)-(5*pi,2)

REM Number of terms to use
for nt=1 to 25
 cls
 print "Harmonics:";nt

 REM Plot squarewave
 pset (0,0)
 for w=0 to 5*pi step .01
  line -(w,sgn(sin(w))),4
 next w

 REM Plot sum of terms
 pset (0,0)
 for w=0 to 5*pi step .01
  y=0
  for k=1 to nt
   y=y+sin((2*k-1)*w)/(2*k-1)
  next k
  y=4*y/pi
  line -(w,y)
 next w

 REM Freeze display (create a gif animation frame)
 delay .2
next nt

Summary

Additive synthesis of a square wave, illustrating Fourier series expansion and Gibbs phenomenon.

See also: Image:Synthesis sawtooth.gif, Image:Synthesis triangle.gif

Licensing

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License. http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

	This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
	You are free: to share – to copy, distribute and transmit the work to remix – to adapt the work Under the following conditions: attribution – You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work). share alike – If you alter, transform, or build upon this work, you may distribute the resulting work only under the same or similar license to this one.
	This licensing tag was added to this file as part of the GFDL licensing update.http://creativecommons.org/licenses/by-sa/3.0/CC-BY-SA-3.0Creative Commons Attribution-Share Alike 3.0 truetrue

• Trigonometric functions