In this triangle two angles, 50⁰ and 40⁰, and the side between them, 9 cm, are known. This is an ASA (Angle, Side, Angle) construction, which can be constructed using a protractor and a ruler.

Shay Shafranek’s electronic ruler is a concept design with a difference. Instead of a boring mockup that only exists inside a computer’s brain, the ruler is a real, working model which lives ...