58 THE MATHEMATICAL PRINCIPLES jB(OK 1. length L is to the same length L diminished by the cosine of the angle AOQ -f- E + G, when that angle is less than a right angle, or increased thereby when greater. And so we may proceed in infinitum. Lastly, take the angle AOy equal to the angle AOQ -f- E 4- G + I -\-} &c. and from its cosine Or and the ordinatejor, which is to its sine qr as the lesser axis of the ellipsis to the greater, \\ e shall have p the correct place of the body. When the angle N — AOQ, -f D happens to be negative, the sign -