In trigonometry an angle is usually drawn in what is called the "standard position" as shown above. In this position, the vertex (B) of the angle is on the origin, with a fixed side lying at 3 o'clock along the positive x axis.

The other side, called the 'terminal side' is the one that can be anywhere and defines the angle. In the figure below, drag point A and see how the position of the terminal side BA defines the angle.

See also Angle definition and properties - Trigonometry

- Angle definition, properties of angles
- Standard position on an angle
- Initial side of an angle
- Terminal side of an angle
- Quadrantal angles
- Coterminal angles
- Reference angle

- Introduction to the six trig functions
- Functions of large and negative angles
- Inverse trig functions
- SOH CAH TOA memory aid
- Sine function (sin) in right triangles
- Inverse sine function (arcsin)
- Graphing the sine function
- Sine waves
- Cosine function (cos) in right triangles
- Inverse cosine function (arccos)
- Graphing the cosine function
- Tangent function (tan) in right triangles
- Inverse tangent function (arctan)
- Graphing the tangent function
- Cotangent function cot (in right triangles)
- Secant function sec (in right triangles)
- Cosecant function csc (in right triangles)

- The general approach
- Finding slant distance along a slope or ramp
- Finding the angle of a slope or ramp

(C) 2011 Copyright Math Open Reference.

All rights reserved

All rights reserved