usually referred as the function COS
Richard C. Buck has written: 'A manual of trigonometry' -- subject(s): Trigonometry 'A manual of algebra'
C. E. Goodson has written: 'Technical algebra with applications' -- subject(s): Algebra 'Technical trigonometry with applications' -- subject(s): Trigonometry
They correspond to the six possible ratios of two sides of a right triangle: a/b, a/c, b/a, b/c, c/a & c/b.
Ralph C. Steinlage has written: 'College algebra and trigonometry' -- subject(s): Algebra, Trigonometry 'S.G. College Algebra' 'SM Coll Alg & Trig' 'College algebra' -- subject(s): Algebra
plane trigonometry spherical trigonometry
The main kinds are plane trigonometry and solid trigonometry. The latter will include trigonometry in hyper-spaces.
One major contribution was that of the Pythagorean Theorem. a^2 + b^2 = c^2
Hipparchus is the father of trigonometry.
TRIGONOMETRY
It is a number - in trigonometry or elsewhere.
Trigonometry is applied in construction and building, as trigonometry measures right angled triangles.
Plane trigonometry is trigonometry carried out in (on) a plane. This could be contrasted with spherical trigonometry, which is trigonometry carried out on the surface of a sphere. Certainly there are some other more complex forms of trig.