Equation being ſubducted there remains z = 2xv + vv. And by reaſon of ſimilar Triangles PS : PR :: NR : NM, i.e. z : v :: y : s = wherein if for y and z we ſubſtitute their values, we get . And ſuppoſing NO to be infinitely diminiſhed, the ſubſecant NM will in that caſe coincide with the ſubtangent NL, and v as an Infiniteſimal may be rejected, whence it follows that which is the true value of the Subtangent. And ſince this was obtained by one only error, i. e. by once rejecting one only Infiniteſimal, it ſhould ſeem, contrary to what hath been ſaid, that an infiniteſimal Quantity or Difference may be neglected or thrown away, and the Concluſion nevertheleſs be accurately true, although there was no double miſtake or rectifying of one error by another, as in the firſt Caſe. But if this Point be throughly conſidered, we ſhall find there is even here a double miſtake, and that one compenſates or rectifies the other. For in the
