Most trigonometry students look at triangles on a flat surface. However, people from ancient astronomers to modern navigators calculated the arc lengths and angles of triangles on a sphere. They used ...

THIS volume gives a systematic treatment of the subject of spherical trigonometry, based on the sound foundation of Todhunter rearranged and amplified. While the merit of the original work is ...

Much of this the author claims to be original, and a great deal, as in the case of the “Plane Trigonometry,” has been collected from the foreign mathematical journals.

New concepts The key purpose of trigonometry is to understand the relationships between the corners and sides of triangles. It is used in areas like surveying, engineering and construction today.

They are great circles with centres at the Earth’s centre. Flights from Paris to Vancouver pass over Greenland, far to the north of both cities, following a great circle route.