3.1 Trigonometric functions

  Topography notes

Trigonometric functions are refer to an angle and they are divisions of a segment with another one. Therefore the value of a trigonometric function is a real number. We consider a plane cartesian coordinate system, a circumference with radius r, a P point into that circumference and a right triangle (OPP”).

  • Sine

  • Cosine

  • Tangent

  • Cotangent

There are another two trigonometric functions, but they are used less:

  • Secant Cosecant

In other contexts and subjects (not Topography), the trigonometric functions may appears defined in another way. Remember that we consider positive the clockwise rotation, instead classical mathematics definition for polar coordinate system consider positive the anti-clockwise rotation. The value of trigonometric functions are positive or negative depend the quadrant which the point is located:

quadrant

sine

cosine

tangent

cotangent

secant

cosecant

I

+

+

+

+

+

+

II

+

+

III

+

+

IV

+

+


Topography notes: Table of contentsby_nc_sa_2
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