Measure of an angle

The notation mZA is used when referring to the measure of an angle (in this case, angle A). For example, if ZD measures 100°, then mZD = 100°. 

Fig. 2-33 Measurement of an angle between twjo poles (Pi and P2 of Fig. 2-26) by measurement of the angle of intersection of the corresponding traces.

The measure of an angle greater than 180° is called a reflex angle. 

This is called the circular measure of an angle and, for this reason, trigonometrical functions are sometimes called circular functions. This property is possessed by no plane curve other than the circle. For instance, the hyperbola, though symmetrically placed with respect to its centre, is not at all points equidistant from it. The same thing is true of the ellipse. The parabola has no centre. 

The ratio, arc/radius, is called the circular or radian measure of an angle. (Radian = unit angle.)... 

Before we can derive a general relationship for the view factor between two finite bodies we must consider and discuss two quantities, a solid angle and the intensity of radiation. A solid angle cu is a dimensionless quantity which is a measure of an angle in solid geometry. In Fig. 4.11-3a the differential solid angle dm, is equal to the normal projection of d/lj divided by the square of the distance between the point P and area dAj. 

Some post-conditions address a particular aspect (e g. the measurement of an angle) and are related to physical phenomena (maximum acceleration), to implementation choices (the last element of a list is always null), etc. 

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