ABSTRACT
The one adopted in this text is to denote vector quantities in bold print. Thus, oa represents a vector quantity, but oa is the magnitude of the vector oa. Also, positive angles are measured in an anticlockwise direction from a horizontal, right facing line and negative angles in a clockwise direction from this line — as with graphical work. Thus 90° is a line vertically upwards and 90° is a line vertically downwards.
