Duolingo isn't just about helping people learn languages anymore. The company has released Duolingo Math on iOS, over a year after it first teased the app. Naturally, Duolingo Math shares a lot of DNA ...

This photograph does a pretty good job of "describing" ripples. But a mathematician could do it with greater precision and predictive power. Image credit: andressolo, Flickr, CC BY 2.0 "How is it ...