Virtual Slide Rules

slide rule Sun-Hemmi No. 153
This is an interesting rule. It was one of the first "vector" rules. The manual calls it "Electrical Engineer's Universal Duplex Slide Rule With Patent Vector Scale, Gudermanian Scale and Log Log Scales." The Gudermannian function converts ordinary trig functions into hyperbolic functions. Mathematically this is a very neat trick.
slide rule K+E 4093-3 Log Log Vector Slide Rule
This is K+E's first "vector" slide rule, introduced in 1929.
slide rule K+E Analon Engineering-Science Analysis Slide Rule
This slide rule does dimentional analysis.