GeoGebra Classroom

# The Equiangular Spiral in Plants - Fibonacci Numbers

With this applet we can measure and count some equiangular (logarithmic) spirals naturally occurring in some plants.
• Click on one check box at the lower left corner of the screen to select an image.
• Drag the image until the center of the spirals is at the center of the coordinate system. The origin is shown with a white point.
• Click on the "Blue" or "Red" check box to show the controls of the measuring spiral.
• Use the sliders to change the coefficient and the angle of each spiral to match one spiral on the image.
• Click on "Count Spiral" button. This will add one to a counter and will leave a trace of the counted spiral.
• Drag the "Rotate Spiral" button to match another spiral on the image. Click "Count the Spiral". Continue this process until you count all spirals in one direction.
• Use the other color spiral to count the spirals in the opposite direction.
Note: For a better control over the sliders, click on a slider and then use the left and right arrows on the keyboard.