The Birthday of William Oughtred (1574) — The Slide Rule and Symbolic Notation

William Oughtred, born 9 September 1574, invented the slide rule around 1622 — a mechanical calculator using logarithms to multiply and divide by sliding two rulers. The slide rule became the engineer’s indispensable tool for 350 years, used to design the Golden Gate Bridge, the Saturn V rocket, and the atomic bomb. Oughtred also introduced the × symbol for multiplication and the abbreviations sin and cos for trigonometric functions — notation still used by every student today.