Inspired by a photo from the art site Colossal (the first picture with the tennis ball.)[br][url]http://www.thisiscolossal.com/2013/07/a-golden-spiral-appears-in-a-wet-tennis-ball-photographed-by-arvin-rahimzadeh/[/url][br][br]Set the Picture slider to 0 to just play with the spiral, as a graph or a traceable point.[br][br]Choose a picture to analyze using the slider. Is it a logarithmic spiral? People are always claiming that spirals are golden spirals - logarithmic spirals with a very specific growth constant. What do you think about that?[br][br]Note: Set b to phi button puts b at that value, not literally at phi![br][br]Other images from wikimedia via [url]http://originalbeauty.wordpress.com/2009/06/27/spirals-in-nature/[/url]

More GeoGebra at [url]mathhombre.blogspot.com[/url].