The quadrant curve or ‘qaus’, is a bow-shaped curve formed from the central quadrant. Grids which come down
from the vertical axis to the curve become the adjacent side of a right triangle which form Pythagoras’ theorem. [See
Figure 1, this side is marked Y]. In the use of the sine quadrant, a grid reading on this scale from the angle of the
curve to the vertical axis represents the value of the ratio of the sine functions. While the grids that are projected
from the horizontal axis to the curve become the opposite side, marked by X in Fig. 1. Grid reading on this scale
from the angle of curve of the horizontal axis represents the value of the cosine ratio functions. Each grid represents
the ratio of horizontal and vertical angles which are read on the curve (0° to 90 °) and centered on the origin of the
quadrant. In Figure 1, the angle θ of the triangle POQ is the angle formed by the ratio of the side adjacent to the
opposite side, while the hypotenuse measures R = 60 units. Hence, the triangle POQ gives the value;
s in θ =
6 0
X (1)
co s θ =
6 0
Y (2)