In this paper we study a type of trigonometric extremal problem which originates in the work of Arne Beurling in the late 1930s and concerns approximations to the function sgn (x). The extremal ...

Ask any professor, and they’ll probably tell you graphing calculators offer a plethora of mathematical uses, like plotting graphs, inputting trigonometric functions — you know, typical academic stuff.

Sure, there are some excellent calculators in the Android Market, but do any of them make you hesitate for a minute when looking at them to figure out whether you are staring at a phone or a smaller ...