Spirograph Bruno Abakanowicz invented the Spirograph between 1881 and 1900. It was used for calculating an area delimited by curves. Drawing toys based on gears have been around since at least 1908, when "The Marvelous Wondergraph" was advertised in the Sears catalog. An article describing how to make a Wondergraph drawing machine appeared in the "Boys Mechanic" publication in 1913. The Spirograph itself was developed by the British engineer Denys Fisher, who exhibited at the 1965 Nuremberg International Toy Fair. It was subsequently produced by his company. US distribution rights were acquired by Kenner, Inc., which introduced it to the United
Geometric function theory Geometric function theory Geometric function theory is the study of geometric properties of analytic functions. A fundamental result in the theory is the Riemann mapping theorem. The following are some of the most important topics in geometric function theory: A conformal map is a function which preserves angles locally. In the most common case the function has a domain and range in the complex plane. More formally, a map, is called conformal (or angle-preserving) at a point formula_3 if it preserves oriented angles between curves through formula_3 with respect to their orientation (i.e., not just the magnitude of the angle).