Now, on the one hand, the setting up of this equation the differentiation has been methodically conceived and methodically executed; on the other hand, the imaginary increments of the coordinates, and the imaginary characteristic triangle formed by them and an equally imaginary increment of the tangent, were invented in order to present the proportionality of the ratio (which was obtained by lowering the degree of the equation) to the ratio of the ordinate and the subtangent, not as something just picked up empirically from something already known, but as demonstrated.