Museo Galileo
Virtual Museum
Reduction quadrant
Reduction quadrant

In Renaissance Italian, quartiere (quarter) was synonymous with "quadrant." The reduction quadrant was generally engraved on nautical quadrants and astrolabes and provides graphic solutions to navigation problems. It is a square (also called nautical square or sinical quadrant) inscribed with a network of lines parallel to the sides and an arc divided into 90°. The instrument serves to reduce the computation of the trigonometric functions for an angle greater than 90° to the computation for an angle lying in the quadrant.