## Product Spotlight: The Sine Quadrant: A Glimpse into the Fascinating World of Graphical Mathematics

2023-07-04

The Sine Quadrant is a graphical mathematics tool that has been invented more than a thousand years ago to perform a wide range of mathematical operations. Developed in 9th century Baghdad, the Sine Quadrant can be used for determining celestial angles, telling time and the calendar, finding directions, as well as the apparent position of any celestial object for any given time. In addition to performing calculations, the Sine Quadrant is an astronomy tool that can be used to take measurements by sighting along the edge and reading the degrees of altitude on the degree scale where the plumb line, installed in the vertex, crossed.

The Sine Quadrant consists of a quadrant and a string attached to its vertex. The string is used to perform calculations by positioning it across the degree scale on the grid drawn from the sexagesimal scales.

The interaction between the sexagesimal scales on the straight edges and the 90 degree angular scale on the arc allows for a range of graphic trigonometric calculations, from the simple finding of a sine, to the complex, dividing or multiplying a sine by a cosine in order to solve not just astronomical calculations.

The Sine Quadrant can be used to measure degrees from vertical or horizontal, determine true vertical, calculate sine and cosine, determine declination for a given day, and perform graphical computations between angles, trigonometric ratios, and sexagesimal values. It can also be used for determining great circle calculations, diurnal arcs, hour angles, azimuths, latitude, and determining cardinal directions. Furthermore, the Sine Quadrant can be used as a map tool to calculate the distance between pairs of for example UTM or MGRS coordinates.

All of these features and their interplay make the Sine Quadrant a powerful and most elegant tool that has been used for over a thousand years to perform a wide range of mathematical operations. The Sine Quadrant is a valuable ancient tool for anyone interested in understanding the foundations of astronomy and its related mathematics in the context in the history of science.

The instrument is available in our store in various designs.

## The Book

The admiration of this instrument lead to writing the definitive book on it: *The Sine Quadrant* is a comprehensive and accessible resource for understanding the graphical mathematics of this arcane instrument to solve primarily astronomical formulas of spherical trigonometry.

The book is an excerpt from the even more comprehensive GQT5 and contains the description of the Sine Quadrant, its tools, principles, functions, and methods, along with an introduction to the required astronomy. It describes instructions for all basic functions as well as advanced methods and graphically developed formulas. The chapters on the functions of the Sine Quadrant provide comprehensive explanations of its completeness as a "supercomputer" for solving any trigonometric problem. The book includes 181 pages, 58 figures, 10 tables, 39 equations, an indexed glossary, and a complete bibliography.

The book is available in our store in English or German as well as on Amazon.