Mathematics · Ch 1 — Angle and its Measurement
Measures of angles
1.1.1
Measures of angles
Measures of Angles
Once a directed angle has been defined by the amount and sense of rotation carrying the initial arm onto the terminal arm, that amount of rotation still needs a numerical measure so it can be stated, compared and calculated with. Two different systems are in standard use for this purpose:
- Sexagesimal system (degree measure) -- the everyday system, built on dividing one complete rotation into equal parts.
- Circular system (radian measure) -- a system built directly from the geometry of a circle, in which the unit of measure (the radian) is defined using the radius and an arc of the circle itself. …
Figure 1.11Two systems of angle measurement
What this figure shows. A side-by-side illustration contrasting a protractor-style degree scale against a circle-and-arc style radian scale, representing the two different systems (sexagesimal and circular) that can both be used to record the same angle's meas …