Article 5
Ratios Expressed as Triangle-measures.

The triangle of a sector and its complementary triangle are measured by the two characteristic ratios. For, let the triangle A1O1P1 and its complementary triangle P1O1B1 be denoted by T1,T1; then

T1 K1 = 1 2a1y1 sinω1 1 2a1b1 sinω1 = y1 b1 , T1 K1 = 1 2b1x1 sinω1 1 2a1b1 sinω1 = x1 a1 . (5)