"Italian psychologist Geatano Kanizsa first described this optical illusion in 1955 as a subjective or illusory contour illusion. The study of such optical illusions has led to an understanding of how the brain and eyes perceive optical information and has been used considerably by artists and designers alike. They show the power of human imagination in filling in the gaps to make implied constructions in our own minds.
Kanizsa figures and similar illusions are a really useful way to encourage learners to 'say what they see' and to explain how they see it. It offers a chance for others to become aware of the different views available in a diagram and share their own thoughts without the 'danger' of being wrong; many people see different things."

"Mathematics is not a series of Statement-Reason proofs punctuated by the occasional "QED". Mathematics, as Paul Lockhart writes in A Mathematician's Lament, is "wondering, playing, amusing yourself with your imagination.""

"Despite what we may sometimes imagine, popular mathematics writing didn't begin with Martin Gardner. In fact, it has a rich tradition stretching back hundreds of years. This entertaining and enlightening anthology--the first of its kind--gathers nearly one hundred fascinating selections from the past 500 years of popular math writing, bringing to life a little-known side of math history."

"Complicated mathematics presented in a generally understandable way Examples from everyday life are mathematized Many examples presented with a good sense of humor Small riddles and conjuring tricks garantee an entertaining reading Imagine that you've finally found a parking space after a long and harrowing search, but are now encountering some difficulty in trying to enter this space."

Expressing a circle in a standard form expression is defined standard equation of a circle. Imagining a circle in a plane at a particular distance from both axis of the Cartesian coordinate system is the standard form of the circle.

On Vi Hart's math concept video creations (graduate of Stony Brook, refers to herself as a mathemusician). She is shown with her balloon icosahedron model