Calculator watch Calculator watch A calculator watch is a digital watch with a built in calculator, usually including buttons on the watch face. Calculator watches were first introduced in the 1970s and continue to be produced, despite falling from their peak popularity during the 1980s. The most notable brand is the Casio Databank series, though watches made by Timex were also popular. Most calculator watches contain only a few number of functions such as +, -, x, / and percents. However, there are several models with additional functions: scientific, including transcendent and trigonometry, in models Casio CFX-200, CFX-400, Citizen 49-9421, and also
Inverse Symbolic Calculator of the tables with 3.702 billion entries (as of June 19, 2010) exists. In 2016, Plouffe released a portable version of Plouffe's Inverter containing 3 billion entries. Inverse Symbolic Calculator The Inverse Symbolic Calculator is an online number checker established July 18, 1995 by Peter Benjamin Borwein, Jonathan Michael Borwein and Simon Plouffe of the Canadian Centre for Experimental and Constructive Mathematics (Burnaby, Canada). A user will input a number and the Calculator will use an algorithm to search for and calculate closed-form expressions or suitable functions that have roots near this number. Hence, the calculator is of great importance