The slide rule was invented around 1620–1630, shortly after the publication of the concept of the logarithm. It is a hand-operated analog computer for doing multiplication and division. As slide rule development progressed, added scales provided reciprocals, squares and square roots, cubes and cube roots, as well as transcendental functions such as logarithms and exponentials, circular and hyperbolic trigonometry and other functions. Aviation is one of the few fields where slide rules are still in widespread use, particularly for solving time–distance problems in light aircraft. To save space and for ease of reading, these are typically circular devices rather than the classic linear slide rule shape. A popular example is the E6B. COUNT 3
QSN1 When was the slide rule first invented? ANS1 1620–1630 QSN2 What is the slide rule used for? ANS2 doing multiplication and division. QSN3 What industry are slide rules still used today? ANS3 Aviation