whoſe given part DF is to be interpoſed between the right lines AB, AC given poſition; then by applying the preceding conſtruction to this caſe, the problem will be ſolved.
Proposition XXVIII. Problem XX.
To deſcribe a trajectory given both in kind and magnitude, given parts of which ſhall be interpoſed berween three right lines given by poſition. (Pl. 12. Fig. 3.)
Suppoſe a trajectory is to be deſcribed that may be ſimilar and equal to the curve line DEF, and may be cut by three rights lines AB, AC, BC, given by poſition, into parts DE and EF, ſimilar and equal to the given parts of this curve line.
Draw the right lines DE, EF, DF; and place the angles D, E, F, of this triangle DEF, ſo as to touch thoſe right lines given by poſition (by lem. 26). Then about the triangle deſcribe the trajectory, ſimilar and equal to curve DEF. Q. E. F.
